The Valhalla Murders (BBC4, 9pm & 9.45pm Saturday)

The nights are drawing in, it's getting colder outside and there's often a touch of mist in the air...

Yes, it's the perfect time for a chilling new TV series to start - although, let's face it, there's rarely a Saturday evening at any moment of the year when such a show isn't airing on BBC Four in its 9pm slot.

Lovers of international crime dramas and mystery thrillers probably have it ingrained on their psyche, automatically turning on the TV just before the opening credits roll.

Channel 4 may have a few gems courtesy of Walter Presents, but BBC Four is really where it's at.

After all, this was the broadcaster that introduced everybody to the grandaddy of them all, The Killing, the Danish cop series following the cases led by Inspector Sarah Lund, whose natty knitted sweater became a cultural phenomenon and a star in its own right.

The drama also helped launch the international career of its leading actor, Sofie Grabol, who has since popped up in the US version of The Killing as well as Fortitude, Gentleman Jack and Us; she can currently be seen alongside Nicole Kidman and Hugh Grant in Sky Atlantic's The Undoing.

The likes of The Bridge, Darkness: Those Who Kill, Wisting, DNA (which reached its conclusion last week) and many more followed, turning Nordic noir and Scandinavian noir into major genres. Examples of dark drama from other countries also appeared, including Cardinal (Canada), Mystery Road (Australia) and Inspector Montalbano (Italy), while the superb Spiral (France) actually predated The Killing by a year.

One of the best chilling series of the past few years is Trapped, an Icelandic offering starring Olafur Darri Olafsson as Andri, a dogged, thoughtful detective who quietly and determinedly goes about his business, no matter what is going on around him.

During the course of two series, we've seen him investigate the murder of a politician and tackle environmental issues; a third run is apparently in pre-production.

While they're waiting for that to materialise, fans can content themselves with another show from the same nation. The Valhalla Murders will be broadcast, as is often the case, in double-bills over the next four weeks.

It's loosely inspired by a true story from the 1940s and introduces us to detective Kata (Nina Dogg Filippusdottir), who hopes to become Reykjavik's chief of police in the not too distant future.

When a drug dealer is found murdered at the old harbour, Kata realises that solving the case could help further her ambitions.

The dead man's girlfriend is the chief suspect until a forensic expert points out the crime could not have been carried out by a woman. Then, when another man's corpse is discovered, Kata's boss suspects a serial killer is on the loose and calls in Arnar, an ex-pat Icelander who's been living and working in Norway.

His arrival is a blow to Kata's professional pride, but if the villain is to be caught, the mismatched duo must learn to work together.

Kirstie's Christmas: Quick & Easy Craft (C4, 8pm Sunday)

Like several of Channel 4's property experts, Kirstie Allsopp couldn't possibly have predicted how her career would pan out.

For instance, George Clarke was a builder and architect before TV came calling and turned him into a heart-throb for renovation-lovers everywhere, while Kevin McCloud was a designer until Grand Designs made him the nation's go-to guru for ambitious self-builders; he's also branched out into other sorts of shows too.

Sarah Beeny, meanwhile, has gone from renovating properties to running an online estate agency and dating service; at the moment she can be seen on Wednesday evenings taking charge of her family's move to rural Somerset.

Allsopp, meanwhile, started out working for such publications as Country Living and Food & Homes Magazine before setting up her own home-finding company in 1996, which concentrated on high-end properties in central and west London.

Then, in 2000, she was thrust upon an unsuspecting world when she teamed up with Phil Spencer to host Location, Location, Location. Several spin-offs followed before she turned her hobby into a successful series.

Allsopp has always been fond of crafts, so she grabbed the opportunity to host Kirstie's Handmade Home with both hands.

"I think it's always interested me, but I never thought I was capable of doing it," she says of the crafting world. "So I would buy it. I'd see something that was made with love and care, and I would purchase it.

"I was a very early advocate of the immaculate Christmas, making a big effort with that kind of stuff. But it was a surprising discovery for me that I was capable of making things myself."

Now she can't seem to stop. She's even set up an annual event, The Handmade Fair, which is held at Hampton Court and offers visitors an opportunity to learn how to make products as well as buy them from the expert.

She's also a major advocate of 'upcycling' - an activity which involves turning unwanted pieces of furniture into desirable artefacts capable of brightening up any home.

So, what crafting activities does she do away from the cameras?

"Anything with a sewing machine I really like," she grins. "Anything where you have to count and concentrate, like knitting, is another matter. I really admire people who do that, I really struggle with them."

During the first lockdown, Allsopp fronted one of the first socially distanced shows, Keep Crafting and Carry On, which was filmed at her own home. Now she's back with a new festive series; in previous years she's hosted Kirstie's Handmade Christmas, which featured competitions and demonstrations, all held in a grand house.

This year, things have had to be a little bit different, but she still hopes to inspire the nation to get making.

Among the highlights to look out for are tips from her florist sister Sofie and recipes from former Bake Off champ Nancy Birtwhistle. But it's her TV 'husband' Spencer who gets the ball rolling with some Christmas cocktails - and if they taste as good as they look, we're all in for a very merry festive season indeed.

Hospital (BBC2, 9pm Monday)

During the first lockdown, many people were reminded of just how important the NHS is to Britain. In those early weeks, a lot of the population chose to show their gratitude with a weekly round of applause, but the nation's broadcasters went further with several documentaries exploring the challenges frontline medical workers faced.

Among the most acclaimed was the two-part Hospital Special: Fighting Covid-19, which was filmed at the Royal Free London NHS Foundation Trust from the first day of lockdown and over the peak of the pandemic.

BBC2 controller Patrick Holland, says: "Hospital Special: Fighting Covid-19 was one of the most candid, challenging and brilliant programmes to have documented this crisis. It has been our privilege to reflect the work of the staff and the lives of the patients at the Royal Free London."

Now though, Hospital is back to find out what happened when normal services began to be re-instated. As viewers who have seen the first two episodes will know, it has presented the medics with many new challenges.

Not only are waiting lists predicted to double by the end of this year but many patients are reluctant to return to hospital, even if they need urgent treatment.

But the series does show just how hard the staff are working to try to get things back on track. Caroline Clarke, Royal Free London Chief Executive, says: "We are delighted to be able to continue working with [production company] Label1 and the BBC following the overwhelmingly positive response from viewers, and our staff, to Hospital Special: Fighting Covid-19.

"Our staff did an incredible job of showcasing the efforts taking place across the NHS in response to this devastating pandemic. Their skill, commitment, kindness and compassion were there for all to see."

She adds: "As we embark on the new challenge of delivering NHS services in a post Covid-19 world, we're looking forward to continuing to share our story with the public."

This week's episode focuses on the impact of Covid-19 on the Royal Free Hospital's transplant services, which treat some of the most vulnerable patients.

A specialist centre for both kidney and liver transplants, it would normally perform around 140 transplants a year in each discipline, but from March, the operations were largely unable to continue.

To add to the pressure, patients with kidney disease who are on dialysis and waiting for a transplant are extremely vulnerable to Covid-19; a quarter of the hospital's dialysis patients who caught the virus during the first wave of the pandemic died.

This episode shows how the service was able to resume due to dropping numbers of Covid cases as well as the implementation of new infection-control protocols.

The department is keen to make the most of this window of opportunity, and has performed three months-worth of transplants in just five weeks.

However, as the hospital sees the numbers of Covid-19 cases rising again, it leads to questions about how long they will be able to offer these life-changing operations.

The Great British Bake Off: The Final (Channel 4, 8pm Tuesday)

Viewers knew when this series of The Great British Bake Off began that there was a chance it wouldn't be like any previous runs.

Not only was there a new presenter in the form of Matt Lucas, who took over from Sandi Toksvig, but it was filmed during a pandemic, which must have created new challenges for everyone involved. For a start, the bakers had to form a bubble.

However, for viewers at least, it has largely felt like business as usual in the tent. Matt hit the ground running, the bakers were as likeable as ever, and returning presenter Noel Fielding and judges Paul Hollywood and Prue Leith seemed unphased by any changes. In fact, for many of us, it has been a welcome weekly dose of normality.

But there is one way in which The Great British Bake Off has felt a bit different in 2020 - the competition has been particularly wide open.

In the first seven weeks, Prue and Paul crowned seven different star bakers, and there have been some shock eliminations. Many viewers would have predicted that Mark and Sura would stick around for longer than they did.

Meanwhile, the somewhat inconsistent Lottie seemed to be coming into her own after picking up Star Baker in Japanese week (admittedly, a week which had some viewers questioning the show's understanding of what constituted Japanese baking), only to be booted out of the tent in the following episode after her 1980s ice-cream cake fell victim to the boiling conditions in the tent.

Now we've reached the final, a favourite may have finally emerged - although it's worth remembering that even the most consistent bakers have lost their nerve at the last hurdle, only for a more unexpected winner to emerge.

So, it's definitely all still to play for as Prue and Paul unveil the last three challenges, which are set to test every aspect of the finalists' baking skills. (Yes, even more so than the week one challenge to make a bust of their celebrity hero in cake form, which produced some of the most extraordinary creations in Bake Off history.)

There's a deceptively simple Signature combining set custard and puff pastry, and a Technical celebrating the classic combination of chocolate and nuts.

Finally, in the Showstopper, the bakers are given free rein to show what they can do as they construct magnificent dessert towers.

The pressure will be on - although hopeful it won't be as stressful to watch as the 2019 final, when Steph, who had seemed to be the one to beat, visibly struggled, ultimately losing to David.

Luckily, it seems that the class of 2020 have enjoyed the experience, with Lottie sharing a letter encouraging other amateur bakers to sign up for 2021.

She said; "I came out of the tent feeling more confident in my baking skills than I ever thought possible and that was all down to the tireless encouragement and coaching from the other bakers, judges, presenters and crew. I love you all so very much. To anyone thinking of applying: DO IT!"

Paul O'Grady's Great British Escape (ITV, 8pm Wednesday)

We may be in the middle of the second national lockdown, with foreign holidays off the cards, but Paul O'Grady is showing us that we don't have to go too far to find adventure and beauty.

To say that the presenter has been surprised by what he's found on his own doorstep is an understatement.

He says: "Kent is known as the garden of England but her beauty has been slightly tarnished lately because all you hear about Kent is lorry parks and operation stack on the M20.

"I think it's about time Kent was given a fair hearing because there's some lovely stuff down here and a hell of a lot I haven't seen, you know."

The latest episode of the domestic travel series sees the Birkenhead-born host explore Kent's stunning coastline that stretches over 350 miles - and hides many surprising secrets.

He starts in Dover Harbour, boarding a speed boat to blast along the white cliffs.

And if you have been watching this series, you will already know how Paul is taken aback by this iconic natural landmark.

When he flew over them in the first episode, he said: "When you see the white cliffs of Dover and you think this is the first thing the pilots saw when they were flying back from a mission in France, they must have breathed a sigh of relief.

"It makes you sort of proud... this should be on the National Health for people with depression - it's just magnificent."

Tonight's particular boat-based journey takes Paul past wartime tunnels and over long-lost shipwrecks before he has an emotional encounter with some of Kent's more unexpected residents - a colony of harbour seals living on a disused MOD navy base.

Back on land, Paul heads further up the coast to the picture-perfect seaside town of Broadstairs, which was once the favourite holiday spot of Charles Dickens.

Paul meets the author's Great-Great-Great-Granddaughter Lucinda and they uncover a remarkable coincidence between their two families and an amazing story about Paul's ancestors murky past.

In 1849, Dickens witnessed the double hanging of Paul's relatives, the notorious Mannings convicted of a murder known as the 'Bermondsey Horror'.

No trip along the coastline would be complete without sampling Kent's most famous seafood export - native oysters.

Braving monsoon conditions, a soaking Paul arrives in Whitstable to meet the West family who have been sorting, selling and shucking oysters for five generations.

A good haul from one boat is 50 oysters, and it seems Paul is tempted to eat the lot in one sitting.

With his taste buds tingling, Paul returns to the white cliffs and the picturesque St Margaret's Bay to seek out more bounty from the sea.

Professional forager Lucia Stuart leads the host on a journey of discovery across the cliff edges and rockpools, and he learns that while mermaid's dust might be acceptable on pizza, brown seaweed tastes like the soul of his shoe.

It has been the year of the staycation, and with travel more complicated than ever and restrictions likely to be slow to lift, there's a possibility that 2021 will much the same.

So perhaps we should all take a leaf out of Paul O'Grady's book, and go in search of hidden gems close to home.

DIY SOS: The Big Build (BBC One, 8pm Thursday)

If you're having a hard time of it and for whatever reason your property is no longer suitable for you and your family, then the sight of Nick Knowles turning up your doorstep must be a very welcome one.

And just to make sure that the recipients of the DIY SOS goodwill know exactly who has arrived at their gaff, Knowles has had a face mask printed with his jaw on it.

That's right, the presenter and former I'm A Celebrity campmate clearly can't bear to cover his handsome mug with a regular mask, and in the first episode of this series, he even had his trusty team wearing one.

Nick and co kicked off the latest run of the makeover series by helping charity Surfability UK, which supports people with learning difficulties and disabilities to surf, to do up their centre.

Then, the series continued last week as they headed to Scunthorpe to remodel Caroline's house after he family suffered two tragic losses.

Both episodes are available to view on the BBC iPlayer.

In tonight's tear-jerking episode (is there any other kind?), the team are joined by hundreds of kind volunteers as they completely transform the home of three orphaned Cornish boys.

After 15 years spent fostering more than 100 children - from premature babies with cerebral palsy through to teenage mothers - Stephen and Lynn Smedley were looking forward to a well-earned retirement in their two-bedroom bungalow.

But then, in April 2017, their retirement idyll was shattered when their beloved 32-year-old daughter Carrie died suddenly, leaving her three boys orphaned.

The grandparents and the three boys are a tight unit, but are living on top of each other in the tiny bungalow.

The three growing boys are squeezed into a single bedroom with a stacked triple bunkbed, which is far from ideal.

Thankfully, the DIY SOS team and volunteers, fuelled by hundreds of pasties, are about to turn this cramped property in Carbis Bay near St Ives into something quite special.

Speaking of the project, Knowles told Cornwall Live: "This family are amazing - the grandparents in their time have fostered over 100 children so if you think about it, they have given over 100 vulnerable children a start in life which is an amazing service for any community.

"Then unfortunately they lost their daughter who passed away and she had three sons herself."

"I think the fact that there's more space will be very emotional for them because it takes a great weight off their shoulders.

"But this doesn't solve all the problems for the family because they are dealing with loss and a lifetime for the kids of growing up without their mum."

One thing's for sure though, seeing Nick and co will brighten up Stephen, Lynn and the boys' day.

And as this particular episode was filmed right back at the beginning of 2019, they will even get to see Nick's real-life face - and not the bizarre masked version.

The Graham Norton Show (BBC One, 10.45pm - Northern Ireland 11.15pm Friday)

We could all do with a bit of early Christmas cheer at the moment.

And who better to signal the start of the holiday season than the undisputed 'Queen of Christmas' Mariah Carey?

Every year, in the build-up to November, she teases her fans, reminding them that there is a point where it's too early to begin playing her classic tune All I Want for Christmas Is You.

This year, the pop superstar eventually answered the annual call of her fans with a Halloween-themed video on November 1, in which a door to a haunted house was opened to reveal Mariah her in holiday PJs and surrounded by Christmas trees and fake snow.

Looking down at her watch, the star sang "it's time", while the unforgettable opening notes of her now-iconic Christmas classic chimed in the background.

Mariah joins Graham Norton tonight to talk about that tradition, as well as her love for Christmas and the success of that timeless holiday staple which finally ascended to the top of the US Billboard Hot 100 in 2019, 25 years after its original release.

It will also be interesting to see what she has to say about her 'Queen of Christmas' moniker, which she initially rejected a few years ago.

"I just don't think I deserve it," she said.

"I'm just a person who likes Christmas, okay? Who happened to write some songs."

However, the main aim of Mariah's chat with Graham is to plug her forthcoming eponymous Magical Christmas Special which will premiere on Apple TV+ this holiday season.

The innovative show will include music, dancing and animation, as well as a line-up of surprise guest appearances.

According to Apple, the event, directed by Bafta winner Hamish Hamilton and Oscar nominee Roman Coppola, will be driven by a universally heartwarming story that brings the world together to "enliven the Christmas spirit around the world".

Also joining Graham tonight is TV chef and writer Nadiya Hussain.

The Great British Bake Off's series six champion is also likely to be popular this Christmas as her new book Nadiya Bakes, which ties in with the series recently shown on the BBC Two, will be high on the bestseller list.

In the publication, Nadiya helps readers conquer cakes, biscuits, traybakes, tarts and pies, showstopping desserts, breads, savoury bakes, and even 'no-bake' bakes - all with her signature mouth-watering twists.

Graham's third guest is British astronaut Tim Peake.

He talks about his autobiography Limitless, in which he aims to take readers closer than ever before to experience what life in space is really like.

Tim also shares his inspiring life story, from military duty in Northern Ireland and Afghanistan to the European Space Agency and the infinite cosmos.

If all that wasn't enough, Take That singer-songwriter Gary Barlow also pops along for a brief natter with Graham before performing the single Incredible, from Music Played by Humans, his first solo album since 2013's double platinum Since I Saw You Last.

Week after week, Graham seems to come up trumps when it comes to pulling in the A-listers.

And with tonight's star-studded quartet plugging a festive TV special, cookery books and a new orchestral and big band album, viewers may think Christmas has indeed come early.

Especially once the Queen (of Christmas) has spoken.