DRAMA Knock Knock marks the Who debut of Mike Bartlett, the award-winning playwright who brought Doctor Foster to BBC1 in 2015 - and he's delivered one of the eeriest episodes in a long while.

Bill and five student buddies are looking for digs. After a series of amusingly hopeless viewings, they're shown round a rambling old pile with an irresisistably low rent. What's the catch? The Landlord (a pallid David Suchet creeping about with a tuning fork) certainly isn't letting on.

Freak draughts, 1930s sockets and no mobile signal are the least of their problems. Creaking woodwork and floorboards and a fright that lurks in the "unsafe" tower are what they ought to be scared of. As night closes in and Bill's friends vanish one by one, can her cool/embarassing "grandfather" come to her aid?

I adore an Old Dark House chiller and this is up there with the finest. It doesn't offer much in the way of black humour, but there are plenty of flesh-crawling thrills. Prepare to develop xylophobia - and irrational fear of wood.