Classification:

After the sumptuous theatrics of Black Narcissus and The Red Shoes, Michael Powell and Emeric Pressburger returned to the muted naturalism of their earlier collaborations for this adaptation of Nigel Balchin's novel about scientists feeling the strain in wartime.

They started shooting the film early in 1948. They shot the location scenes first, in Dorset, where they did the brilliant bomb-defusing sequence climax. It was a long and difficult sequence, most of it shot at about 5 am in early March with a biting east wind coming in off the sea. And the artificial foot the lead star, David Farrar, wore to play the part of Sammy Rice was so uncomfortable that he couldn't help limping anyway.

The climax aside, Powell & Pressburger were obviously uninspired by the lengthy passages ofchat in which the backroom boffinsbicker about their latest inventions, but their masterful use of camera angles and cutting gives the finale anunbearable tension and almost makes up for the length of time it takes to get there.

Other strong points in the movie is the beautifully enigmatic presence of Kathleen Byron though her character is somewhat underdeveloped and the sulliness of David Farrar. Lordy, he was one actor who the description of 'impenetrable' could be applied and was as cold as stone.

Perhaps the weakest point of the film is the surreal sequence in which the complex Sammy seeks solace with a giant whisky bottle. Surrealistic scenes have always been notoriously difficult when placed in the confines of a 'straight' story and this one is no exception. It adds nothing to our understanding of Sammy.

Watch out for an exquisite cameo from Renee Asherson.

• The Small Back Room: UK Dvd