Margot and Fergus Henderson at Joe Allen

As a lad, my father would take me to eat at Joe Allen, the enduring West Side gathering place in New York’s Theatre District. He invariably ordered us burgers and not because it was the restaurant’s least expensive main dish. Most of the Broadway personalities seated near us knew to order the burger, too. It was the best thing on the menu.

The father of the great English chef Fergus Henderson of St John Restaurant fame also took his son to the great theatre-land haunt and also insisted he have a burger.

The happy discovery of Fergus and my shared boyhood experience was undimmed by two differences in our stories: First, Fergus’s father took him to the Joe Allen in London’s West End, not the one on Manhattan’s West Side. Second, the Joe Allen burger of his memory was never the best thing on the menu. It was the best thing off the menu: In London the burger has always been unlisted – the worst kept secret around Covent Garden.

I encountered Fergus this week at the London Joe Allen, sharing a table with his wife Margot Henderson, the chef at Rochelle Canteen, and trying the guest burger she had created for Joe’s. Her Margot burger, one of four burger collaborations to be featured at Joe Allen this month, consists of a Swaledale chuck mince patty layered with roast and raw beetroot, roast red onion, watercress, green sauce and Rochelle ketchup on a St John bun.

As good as Margot’s on-menu burger is, I secretly wanted the off-menu burger Fergus and his dad enjoyed all those years ago. And now I’m hankering to take my son to Joe Allen and – what else? – insist he polish off one, too.