Foyle's War, Series 8, ITV

Always a treat to see the shrewd, penetrating gaze of DCS Christopher Foyle back for one of its all-too-brief runs, though no doubt rationing Foyle's War to short series at long intervals is what has enabled writer/creator Anthony Horowitz to sustain it for so long. The three episodes in the new Series 8 find Foyle back in Britain, following a trip to the USA to "tie up some loose ends" from a previous case.

It's 1946, and he's becoming embroiled in the Cold War as East faces off against West and rampant paranoia stalks the corridors of power. One of the strengths of Foyle has always been the way it inhabits its period setting quite naturally, rather than battering you over the head with Glenn Miller tunes or fashion parades of pristine Forties costumes, and that tradition is being maintained.

'Foyle's War' is unthinkable without Honeysuckle Weeks's portrayal of the doughty Sam

The post-war London in which Foyle (Michael Kitchen) found himself enlisted to help MI5 unpick a Russian spy ring felt like a sad and weary city, with any triumphalism about trouncing the Hun already replaced by Stalin-related anxiety. The episode opened with an American atom bomb test in New Mexico, but the Russians are hell-bent on closing the gap and MI5 have uncovered the "Eternity Ring" of spies trying to infiltrate the British nuclear programme.

And why would MI5 recruit  a humble policeman from Hastings? Because they've acquired a photograph of Foyle's former driver Samantha Stewart, now working as assistant to the nuclear physicist Professor Fraser (Stephen Boxer), which seems to show her exchanging documents with a spy named Vlessing outside the Old Vic theatre.

The unlikeliness of this device will be overlooked by Foyle regulars, since Foyle's War is unthinkable without Honeysuckle Weeks's portrayal of the doughty Sam (pictured below)... but she's changed. She's now Mrs Wainwright, having married Adam, a prospective Labour candidate for a seat in Peckham. She looks older and worn out, struggling to put food on the table in rationing-stricken Britain ("sometimes you wonder who really won the war," she muttered). The scene in which she was vetted by a Labour Party panel as a prospective candidate's wife was a hilarious exhibition of political incorrectness as she forgot the name of the constituency and couldn't bring herself to endorse Labour "values".

Meanwhile Foyle was showing the spooks - a pompous, supercilious crew afflicted with laughable delusions of competence - how to run an investigation. Kitchen's Foyle remains a small masterpiece of restraint in which a skilfully-deployed eyebrow or a twitch of the lip can be deadly weapons, while his clipped one-liners through gritted teeth convey a message of "you should know this already, moron, but I'm just going to remind you". Horowitz also manages to root Foyle's deductive skills in his attentiveness and ability to listen, rather then pulling absurd rabbits of hats, although one vital clue this week was unusually obvious. Suffice to say that it didn't take Foyle long to out-think the cynical but blundering spycatchers - headed by Hilda Pierce, played by Ellie Haddington rather in the mould of Alec Guinness in The Ladykillers - and his reward was to be recruited for more intelligence work. With Sam alongside, of course.