Stupendous turn from Romola Garai in the lead role but, while this sets up intrigue and atmosphere well, the plot devices creak audibly towards the end.

A political yarn - sometimes creepy, sometimes daft - in the Hitchcockian vein.

For all its sumptuous production design, Steven Poliakoff's tale of glamorous toffs and treason is so laboured and slow that it's practically pensionable.

Poliakoff's film has provocative ideas about appeasement and a few truly chilling sequences, but some surprisingly clumsy dialogue and occasionally awkward acting suggest he hasn't fully got a grip on his material.