This should have been a really good film. An examination of English upper class life at the end of the summer of 1939, in particular how there was a strong faction in favour of appeasement with Hitler rather than going to war, couched in the form of a thriller, could have been superior and intelligent entertainment. But this effort is saddled with some of the clunkiest dialogue I’ve heard in months – the kind designed to ensure a dumb audience is fully aware of what is going on - and some of the most clichéd direction. Both from Stephen Poliakoff, who has something of a decent track record.

Very briefly: Anne is the adopted daughter of Tory MP Sir Alexander Keyes, and works in London on the West End Stage and in movies. But at the idyllic family estate in Norfolk funny things are afoot – she discovers secret government recordings disguised as commercial 78’s, and the plot inexorably thickens. As this long-winded saga grinds along it becomes increasingly preposterous and convoluted.

A starry cast do what they can with this intractable material, but only Romola Garai in the lead, Charlie Cox as her boyfriend and David Tennant as an outspoken junior MP bring any life and veracity to their roles. Bill Nighy delivers a performance so wooden you want to knock nails in it. The costumes are fabulous, production design good and the cinematography, mostly gorgeous.

What this film desperately needed was a really hard-nosed producer saying to the creatives, “Never mind your reputations, unless we pull this round it’s going to be a complete turkey.” And why does this matter? Look at the opening credits. This is a BBC film supported with funds from the National Lottery. It’s our money they wasted.