Expensive BBC4 dramas have become known in recent years for being about style over substance; often with some very fine acting, but commonly underwhelming, despite the obvious investment in what is, unarguably, the BBC’s most niche entertainment channel.

Adapted from the novel by Alan Furst, Spies of Warsaw is the latest in this line of ambitious drama commissions for the channel, starring Britain’s most attractive scarecrow David Tennant as Jean-Francois Mercier, a cunning but moral French secret agent in late 1930s Warsaw.

Mercier has quite a lot on his plate – the neighbouring Nazis are getting a bit uppity and even his own countrymen don’t trust his capability to save the day.

Presented in two feature-length episodes, the first part makes no attempt to thrill. Held together by taut atmospheric direction, the drama prefers to build intrigue slowly, mirroring the slow and reluctant descent towards war. This can, at times, make it a labour to watch, particularly with the lengthy running time (90 minutes), but the remarkable supporting cast sustain interest, with particular praise for Anton Lesser (The Hour) as the enigmatic Doctor Lapp, and Fenella Woolgar (St.Trinians) as a sassy Parisian socialite.

Of course, “mum’s favourite” David Tennant is the steadfast and sexy glue that holds the whole thing together – he lopes through the narrative in an array of aesthetically pleasing gentleman’s wear, romancing ladies and generally looking like a slightly unwell James Bond.

This is one of his most high profile jobs since leaving Doctor Who, and it’s a good choice – the character of Jean-Francois Mercier is some distance from his somewhat zany, increasingly upset Doctor, allowing Tennant to demonstrate that he is still undeniably capable of leading such a talented cast.

The first episode ended on a well-executed cliff-hanger, with the concluding sequel going out on Wednesday 16 January at 9pm on BBC4. Tune in to find out if plucky Jean-Francois can save the woman he loves and avert the ceaseless march of war. Spoiler alert: Probably not.