National Treasure (Channel 4, 9pm)

'YOUR life falls off a cliff," Robbie Coltrane says about the experience of being a national treasure playing a national treasure accused of a historic rape.

In this four-parter, Coltrane plays fictional comedian Paul Finchley who used to be half of a successful double act and is now a teatime quiz show host. Now, he has the police knocking on his door concerning the alleged rape of a young woman in the 1990s. "the first episode is not about whether he did or didn't do it. It's about what it would be like for any of us if somebody came to the door and said you had raped somebody 20 years ago. So he's a man at the end of his tether and is totally humiliated.

"You have to imagine what is would be like to have 20 guys at the bottom of your garden, tabloids talking rubbish and people spitting at you. But it gets more and more ambiguous, dark and strange as it moves. I think viewers' opinions will keep shifting all the way through."

He confesses he went straight to the end of the script to find out if Paul was guilty, but admits that he couldn't pass over the role because it allowed him to work with another national treasure, Julie Walters. The two spent two weeks rehearsing the roles of Paul and wife Marie, who is deeply religious and, at least publicly, decides to stand by her husband.

North-East actress Andrea Riseborough plays their recovering drug addict daughter Dee as the allegation impacts on her life and her two young children.

"These cases have been a big part of our current affairs for the last few years," says 66-year-old Walters. "But it's always the wife that makes me think, 'Gosh, I want to know about her'. Marie is quite conservative, she has her own problems and her daughter is wayward, so they a difficult relationship, but she's a very kind woman and I admire her strength. You do think, 'How can she be with him'? Whether he's done this or not, a string of infidelities have gone on throughout their life. If it was me, he would out the door. I can't bear any kind of lying, but Marie's not like that, so it was really interesting to do."

Robert Webb, Frank Skinner and Alan Carr make cameo appearances in what promises to be a gripping drama.

Coltrane says: "In the programme, my character does this interview with Victoria Derbyshire... Finchley's argument is 'Why does this have to be done in public?' And she says 'Well, what do you think? Should the law be protecting the wrongfully accused, or those who have actually been abused? Because that's your choice'. "

The Hairy Bikers' Chicken and Egg (BBC2, 8pm)

DAVE and Si cook chicken tagine with preserved lemons and olives for some rebel Berbers in the mountains north of Fez in Morocco, and experience the full extent of Spanish and Moorish influences on Moroccan cuisine in Tetouan – the gastro and poultry capital of the country. The boys also make their own rose and pistachio ice cream to cool down after a visit to a Hamman and are taught how to make a special pastry for their piece de resistance – chicken pastilla pie.

Alex Jones – Fertility & Me (BBC1, 10.45pm)

IF you're a childless woman in your mid-to-late thirties, you've probably seen all those articles warning you about the "biological clock" and the dangers of waiting to become a mother. Alex Jones is no exception, so when she married her husband, Charlie, last year and decided to start trying for a baby, she was worried that at 38, she might be one of the 3.5million people in the UK who struggle to conceive. Here, Alex investigates what pioneering science is doing to help people struggling to become pregnant and travels the world to see the cutting-edge techniques that could revolutionise fertility treatment in the future and give everyone new hope of having children.

Viv Hardwick