Close to the Enemy (BBC2, 9pm)

IN this concluding episode, it looks like it really is time for Rachel, played by Stockton's Charlotte Riley to get serious as Callum (Jim Sturgess) worries he's been caught up in a game and pressures her to confess her true feelings for him.

Meanwhile, as preparations for the wedding get under way, Kathy (Phoebe Fox) finally confronts Bergit (Antje Traue) about her activities, which makes the prisoner realise that she's running out of options. Harold (Alfred Molina) makes a decisive move and Victor (Freddie Highmore) continues to be haunted by the effects of the war.

Riley's glamorous American has been one of the stand-out characters in the series, particularly thanks to the impact of her outfits

in austerity Britain. "Her costumes are amazing. She's a millionairess, so she gets to wear fabulous clothes. Rachel is very fashion-forward. She's wearing clothes that are from the early 1950s; everyone else is stuck in the mid-1940s. She also wears fabulous hats – I don't think people wear enough hats these days. My favourite piece is a strapless taffeta ball gown in gold and green. It's really beautiful. I have to admit, I felt quite glamorous that day," says Riley.

However, the frocks weren't the only thing that attracted her to the role – there was also the chance to work with the series' acclaimed director and writer.

"The scripts were fantastic, but the biggest draw of all was working with Stephen. Ever since Gideon's Daughter, I'd always wanted to work with him. It's been a dream of mine. I'd watch his films and think, 'I'd love to be in that'. I have friends who have worked with him, and they have all had a great time."

Riley's previous credits include Peaky Blinders and Jonathan Strange & Mr Norrell says she's been careful to make sure that her character hasn't been having too good a time. "She's an American, and she just has a natural effervescence. She is charming, but she can often disarm people with her front-footed-ness. In this drama she makes everybody wake up and smell the coffee, in a gentle way. She creates a lot of the fun in this piece. All in all, she was a great character to play.

"She has to tread a fine line between being a breath of fresh air and treading on the toes of people still reeling from the grief and pain of war. She tries to be the life and soul of the party, but at the same time she doesn't want to offend people who might ask, 'What are you celebrating for?'"

Who Do You Think You Are? (BBC1, 8pm)

THE Royle Family star Ricky Tomlinson sets out to trace his family tree. The actor is well known for playing the archetypal scouser – and it turns out his Liverpool roots run deep. Tomlinson discovers that he comes from generations of carters, who transported goods on Liverpool's docks when the city was the British Empire's busiest port. His rage and sorrow grow as he discovers how dangerous conditions were for his ancestors, eerily echoing his own fight for workers' rights as a trade unionist in the 1970s.

The Secret Life of the Zoo at Christmas (C4, 8pm)

WITH Christmas fast approaching, the keepers try to get the animals into the festive spirit. Stockings have been hung for the Sumatran orang-utan family, only for eight-year-old Indah to open everyone else's. There is concern about the health of reticulated python Bali, who has been off her food for more than three months. She needs a check-up, but at 23ft it takes ten brave keepers to catch her. Malayan tapirs Marjorie and Bitong welcome a baby, however the new dad is not happy when his daughter comes between him and his partner, and sun bear couple Tony and Millie's relationship is growing stale – will a trial separation help?

Viv Hardwick