As Sergeant Wilson in Dad's Army, John Le Mesurier was the epitome of insouciance and languor. Cuffs undone, a half smile on his lips, oozing charm for the ladies to the pompous bantam cock that was Captain Mainwaring everything about his deputy spoke lounge lizard rather than soldier.

The real life of John Le Mesurier, as this authorised and definitive biography shows, was rather more complicated. To some extent Sergeant Wilson was indeed Le Mesurier playing himself: a man who prioritised a thorough perusal of the Racing Post in the morning before buckling down to rehearsals; who once sweet-talked a make-up girl into taking his watch off his wrist, winding it up for him, and tenderly putting it back on; from whom his friends would receive an early-evening phone call at witching hour consisting merely of a murmured, 'Playtime...?'

But while his acting career, ranging from I'm All Right Jack to Brideshead Revisited, found a glorious and sustained Indian summer in the greatest situation comedy British television has ever produced, in his private life this mild, quietly-spoken, decent man was plagued by turmoil and heartbreak. Married three times, he saw his first wife succumb to alcoholism, his second - the comedy diva Hattie Jacques - move her lover into the family home, and his third (though devotedly caring for him to the end of his life) enjoy a passionate dalliance with his former screen colleague Tony Hancock.

Ultimately, as this sympathetic and moving book shows, John Le Mesurier was a far more courageous, profound and admirable man than Sergeant Wilson was ever meant to be, and is immortalised in the ubiquitous repeats of Dad's Army.

First published: Saturday 25th September 2010