The writer E.B. White believed that analysing humour was like dissecting a frog: few people are interested, and the frog dies. All week, I’ve been wondering why Dad’s Army makes me weep with laughter. The popular theory-the British class system + eccentricity + a Home Guard platoon = hilarity doesn’t convince me. What lies behind humour is so evasive, so fragile and so mysterious that if you could sum it up in a simple formula, we’d be laughing all the time.

Meanwhile, my sense of humour is on hold. The man who was a genius at making me-and everyone I know-laugh died last week. He may have been a national hero, but, in this patch of Suffolk, David Croft was our next-door neighbour. We’re 10 or so miles from the Stanford Battle Area near Thetford where the War Department allowed the makers of Dad’s Army access to fields and woods for £5 a day. We’re three miles as the crow flies from Honington, where lies the Crofts’ homestead-a rambling Elizabethan manor house with room for Ann, his beautiful and brainy wife, their seven grown children three daughters, who all got their mother’s looks, and four sons-and their various spouses and countless grandchildren.

One common belief about humourists is that, deep down, they are melancholy souls. In David’s life, you don’t have to go far to hit the not-so-funny bone. The younger son of actor Reginald Sharland and musical comedy star Anne Croft, David was nine years old when Reginald left for Hollywood. He never saw his father again. And yet, reading his autobiography You Have Been Watching…-the feeling that floods through the pages is that this is a man who can’t believe his astonishing good luck. Even his lacklustre school days, first at Arnold House in St John’s Wood, then at Rugby School, years in which he won only one award ‘the smallest EPNS silver cup ever manufactured’-presented to him for impersonating Jack Hulbert singing The Sun Has Got His Hat On in a talent competition, left him undaunted.

When financial troubles meant leaving Rugby early, his mother enrolled him in singing and dancing lessons, as well as a secretarial course where he mastered touch-typing. He believed his typing skills made him a writer. He even credits luck to his serious illness when serving in North Africa during the Second World War. Sent back to England to recover, he managed to get onto an officer’s training course and, by the war’s end, he had served in India and Singapore. By the age of 23, he had risen to the rank of major.

Perhaps all stardust has the elusive element of luck. When his father left, he and his older brother, Peter, took their mother’s maiden name. I suspect David Croft has a more memorable ring to it than David Sharland. If the red-haired young man who acted in many West End musical come-dies had been more successful, he might never have become a BBC executive, never become a comedy producer and writer.

But the real Eureka moment in his life was his marriage to actress and theatrical agent Ann Callender, ‘the architect of my life and happiness’. A great beauty with the star quality that makes heads turn, Ann gave David the large family he longed for while steadily guiding his career. She persuaded him to see an actor she represented who she thought was right for a panto David was directing. The actor was Jimmy Perry, who became David’s collaborator on Dad’s Army, Hi-de-Hi!, It Ain’t Half Hot Mum and You Rang, M’Lord?

In August, the Crofts gave a party at their home. Predictably, it was a great production: glamorous dresses, two bands, delicious food, endless Champagne, three generations, old friends, dramatic fireworks. In fact, it was a perfect farewell party: lavish, generous, fun. Only a genius, a lucky genius, could get the timing so absolutely right.

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