A Culture Show Special: Hilary Mantel, BBC2, Saturday<br/>Planet Dinosaur, BBC1, Wednesday

Big monsters savaging small monsters is always popular &ndash; and this lot certainly have the ex factor

Wouldn't you love to be a fly on the wall when the telly people work out the schedules? Take last night. It doesn't get more primetime than 8pm on a Saturday in September, as the nights draw in and nobody can afford to go out. So I wonder who at Channel 5 decided that was just the moment for a second-rate 1960s war movie. "How about The Bridge at Remagen? And let's start it at 6.25pm, so most people catch only the last hour ..."

Still, when you're up against a new series of The X Factor on ITV, and River Cottage on C4, I guess you cling to minority appeal. Which must be why we got a rare burst of highbrow on BBC2, with a A Culture Show Special, plonked between repeats of Dad's Army and QI.

It was an hour to savour: a beautifully shot, intelligent and memorable interview with the novelist Hilary Mantel, by the documentary-maker James Runcie. We've all heard of Mantel, even if we haven't read all 12 of her books. She's been writing for nearly 40 years, but hit the big time in 2009 with Wolf Hall, a 672-page blockbuster set in the court of Henry VIII which won the Booker.

As with the best biographies, you didn't have to know Mantel's work to find her story affecting. It was told like a ghost tale, all spooky music and shots of Tudor buildings. This might have been because Tudor buildings are her territory (one reviewer once snitched that she wrote too much about wallpaper). Or maybe because Mantel believes in dark forces: she felt one once, aged eight, standing alone in her garden, which she described as "the essence of evil".

Now 59, she still speaks like a little girl, slowly and deliberately. Those wide eyes mask a formidable brain: aged 22, she started writing an 800-page epic about the French Revolution, A Place of Greater Safety. Not the obvious career path for the daughter of Irish immigrants raised in a Derbyshire mining village.

The bombshell is that Mantel suffers from a debilitating condition, endometriosis. The endometrium is the lining of the womb, a special kind of tissue that is shed every month; in sufferers, this tissue spreads beyond the womb, causing bleeding, pain and nausea. After years of feeling ill, and being dismissed as neurotic by doctors, she was finally diagnosed aged 27 and immediately had her ovaries removed. This left her unable to have children and plunged her into the menopause: "It was worse than one could ever have imagined."

Not that she lets it get in the way. Mantel has lived in Botswana and Saudi Arabia, has married the same man twice, and knows enough about topics as diverse as Irish giants and Muslim fundamentalism to have written novels about them. Today, her life is deliberately dull. "You need to lead a boring life if the contents of your head are very exciting," she explains. "You can't have excitement in every part of your life." It could be a TV scheduler's maxim.

Not for BBC1: they're keeping us on the edge of our seats with a new season on dinosaurs. Planet Dinosaur is being billed as the new Walking with Dinosaurs, the superb series of 1999, narrated by Kenneth Branagh, at the time the most expensive documentary series per minute ever made. That was 12 years ago, and CGI technology has leaped ahead.

But this isn't just any digi-whizzy documentary – John Hurt does the narrating. No dinosaur jokes, now. Actually, Hurt's perfect: he can do science and suspense.

Episode one took us to Africa, where we met two dinosaurs who were bigger than Tyrannosaurus rex: the spinosaurus and the carcharodontosaurus. As the blurb puts it, "Planet Dinosaur features a cast of new dinosaurs that will feed the nation's nightmares." The visuals are certainly every boy's fantasy – I'm only glad nobody thought to make it in 3D. You do get some science thrown in – fossils discovered in 2008 suggest the spinosaurus had underwater sensors in its mouth for catching prey, a bit like a crocodile. But really, Planet Dinosaur is just an expensive excuse to show a few big monsters savage some smaller ones. A bit like The X Factor – why not move it to Saturday night?