Flare Path, Theatre Royal, Haymarket, London

Given Sienna Miller's dismal track record in this neck of the woods (a wooden Celia in As You Like It in 2005), her return to the West End seemed about as welcome as yet another juke-box musical or a further hike in the outrageous price of an interval drink. But her performance as the conflicted actress-heroine of Flare Path is genuinely heart-tugging in the subtle way it communicates this young woman's struggle between patriotic duty and extra-marital desire (in fact it makes those terms seem altogether too bald).

That's just one of the many marvels in Trevor Nunn's richly entertaining and beautifully judged revival of this theatrical rarity. His production is a most valuable contribution to the current Terence Rattigan centenary celebrations. Written in 1941, staged in 1942 and clearly informed by its author's experiences of the RAF as a tail-gunner in the Second World War, Flare Path was the work which proved that Rattigan (who had not had a real stage success since French Without Tears in 1936) was not a one-hit wonder.

The action is set in a hotel near a Bomber Command airbase in Lincolnshire. In a Forties hairdo and high-waisted trousers, Miller cuts a striking figure as Patricia, an actress who, after a whirlwind wartime romance, finds herself married to Harry Hadden-Paton's superb Teddy, a boyish, endlessly affable Flight Lieutenant with the deceptive manner of an upper-middle-class chump. On this particular weekend, Patricia had been planning to tell him of her decision to leave him for her former lover, Peter Kyle, an English-expat Hollywood star. Her resolve is weakened, though, and Rattigan sets this painful predicament in the context of other tricky war-time relationships. The luminous Sheridan Smith keeps bringing delighted laughter and a lump to the throat in her superb portrayal of Doris, the down-to-earth Lincolnshire barmaid elevated to foreign aristocracy by her marriage to Mark Dexter's wonderfully quixotic, Anglophonically-challenged Polish Flying Officer, Count Skriczevinsky. His first wife and his children have been slaughtered in Europe. Will his bond with Doris survive the war? Smith wrings your heart as she conveys the pluck and refinement of spirit of this superficially common little woman.

Everything that could be contrasted in the lurid acrylics of melodrama in Flare Path is saved by moments where the chosen medium seems to be the smudged subtlety of drawing in coloured chalk. This is true not least of Miller's performance. There's a riotously funny, knees-up happy ending – an occasion into which, after the lonely pang of watching the Hollywood lover depart, Miller's Patricia allows herself to be absorbed by authentically life-like degrees. A terrific evening.