DOCTOR WHO, BBC1, Saturday 6.45pm

As we all know, the Doctor isn't the type of guy you're going to forget in a hurry. For a start, he's always dashing about at 100 miles per hour, and spends much of his time saving the world from monstrous beasties.

Somebody else who spent most of her life up to her elbows in grisly goings-on was Agatha Christie.

Okay, so the activities she encountered were only created in her imagination and committed to the pages of her many murder mystery novels, but she knew a thing or two about death and destruction, even if it was only ever Earthbound. Or was it?

In 1926, following the publication of The Murder of Roger Ackroyd, which is now widely regarded as her masterpiece, Agatha's first marriage, to World War One hero Archibald Christie, ended when her husband fell in love with another woman.

The writer then famously disappeared for 10 days and is believed to have spent time at a hotel in Harrogate, checking in under her love rival's name. Little is known about this period – the author herself failed to mention it in her autobiography, although she did claim she was found to have been suffering from a nervous breakdown.

Various theories have abounded ever since, including that her disappearance was nothing more than an elaborate publicity stunt; the 1979 film Agatha (starring Vanessa Redgrave in the title role, Timothy Dalton as her estranged husband, and Dustin Hoffman as the American journalist sent to find her) offers a fictional view of what may have happened.

Intriguing

Nevertheless, nobody really knows, and although it seems unlikely that the idea put forward by The Unicorn and the Wasp – the title of this week's episode – could be true, it's certainly an intriguing take on the event.

According to the tale, Agatha was out of circulation because she was helping the Doctor save the planet from a revenge-seeking Vespiform – or giant alien wasp, to you and me. No wonder she felt in need of a rest away from the hustle and bustle of the roaring Twenties!

It's not the Doctor's first meeting with a real-life individual, for a start he crossed paths with Charles Dickens in 2005's The Unquiet Dead, but rarely has he had an adventure as inventive as this.

"Visiting Agatha Christie has been on my wish-list for ages now and, for the Doctor, it's a real meeting of minds," says Russell T Davies, Doctor Who's executive producer and head writer.

Agatha's grandson, Mathew Prichard, is just as excited about the project: "What a brilliant idea that Agatha Christie and Doctor Who should meet! Two characters whose contribution to British entertainment is absolutely unrivalled.

"As far as I know my grandmother, Agatha Christie, never saw Doctor Who, but I am sure she would have been intrigued, excited and above all flattered by all this attention in 2008."

Fenella Woolgar guest stars as Ms Christie, while Felicity Kendal also appears alongside regulars David Tennant and Catherine Tate.