In July 1968, the well-known war photographer Don McCullin was commissioned to photograph the Beatles in different locations around London, for a session known as the Mad Day Out. It was for Life magazine. I think they moved around a lot to avoid big crowds gathering.

This is St Pancras Old Church and gardens, in north London, where some of the best-known pictures were taken. My grandad, Jack, was the head gardener. He was visiting family in Derbyshire that day: he always said if he had been there, he wouldn’t have allowed the Beatles in, because they were the sort of “long-haired layabouts” he disapproved of. He was upright and Victorian, dressed in corduroy trousers, waistcoat, jacket and tie, even when he was working.

I’m the little boy on the left in the light blue jumper, and I’m six years old. Standing next to me is my younger brother Neil and behind us is our nan, Eunice. She’s holding paper and a pencil, as we got three of the Beatles’ autographs. Yoko Ono, who was there that day, kept calling John Lennon away, so we only got Paul, George and Ringo’s signatures. As young boys, we lived on and off with my grandparents for years, staying with them before we were finally offered a council flat in Shepherd’s Bush, west London.

There was no announcement that the Beatles were coming – they just turned up, with a small group of friends, assistants, photographers and hangers-on. The other kids were just knocking about in the park that day, as we were. King’s Cross and St Pancras was a poor area then; parts of it were Dickensian. According to my nan, I sat on Paul’s knee. At one point, she brought them out tea.

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It was a beautiful park, much bigger than it is now. There was a Victorian bedding scheme, which my grandad was very proud of, a fountain, glasshouses, a playground, London plane trees. Sir John Soane’s mausoleum is there. In one famous picture, the Beatles are posing among my grandad’s prize hollyhocks. He had eight or nine staff, some of them in this photograph – the older man in the trilby at the back was the park keeper. He would take us to different London parks – Parliament Hill Fields, St James’s – and point out plants and birds. I got my love of the outdoors from him.

A black and white version of this photograph, by another photographer who was there called Stephen Goldblatt (although it’s often attributed to McCullin), features on the inside gatefold sleeve of two Beatles compilation albums: the Red Album, from 1962-1966, and the Blue Album, from 1967–1970. I’ve no idea why it was chosen: I suppose it’s nice the way they are mingling with the crowd, looking like normal people. I first saw it on one of the records at a girlfriend’s flat when I was 16: I said, “That’s my nan!” And then, a few seconds later, “That’s me!”

This photograph was published for the first time in Don McCullin’s 2010 book A Day In The Life Of The Beatles. Looking back at it today, I remember those austere times, my London roots – and the huge back garden we were lucky enough to play in.

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