Bailey is short, fierce-eyed and direct: "I just don't want it to be s***!" he says.

I had spotted the photos which inspired We'll Take Manhattan in a weekend magazine a few days earlier - beautiful, rather innocent pictures of Jean Shrimpton, 18, on the wintry streets of Manhattan in February 1962.

I had sensed in the accompanying article the sniff of a story - of young Cockney upstart Bailey being offered a big assignment by Vogue, and risking everything by insisting on using his girlfriend, Jean, against the specific wishes of his fashion editor, the fearsome Lady Clare Rendlesham.

Young love, bad behaviour, the beginning of a revolution... And now here I was, with Bailey's dog in my lap, trying to convince one of the most fearsome survivors of the fashion and photography world - the man who did the wedding photos for the Krays - that he should allow me to noodle around with his legacy.

If I had known then what I know now, I would probably have been more nervous.

Bailey has the intellect of a nuclear physicist - mighty, knowledgable, always questioning - in the body of a Mile End barrow boy, with his Cockney cut-your-knees-off-and-then-we-can-talk humour still intact.

Jean Shrimpton scrupulously avoids public contact, having retired from modelling in the early 1970s.

And portraying their life of 50 years ago, in London and New York, on a slender budget, would drive me and my tiny crew to the giddy limits of our ability.

The best part of making the drama was the detective work: the 20 or so published photos from their breakthrough NYC photographic session acted as a series of clues as to where they went and what they were doing.

By looking closely at the details, we were able to work out many of the exact spots where the shots were taken - and go there, to make the drama behind the camera.

Existing footage of young Bailey and Jean at work told us how they talked. Lady Clare, now deceased, was also kind enough to take part in a 1964 documentary, Fancy Dressers, which proved invaluable for Helen McCrory in catching her mix of tiger and butterfly.

The funniest part of filming was the Brooklyn Bridge. Bailey and Jean shot there ("it was so cold the camera stuck to my fingers") and so did we, but on a hot day - with my crew of 10 trying to politely hold back several hundred joggers, cyclists and tourists in 35C heat so we could complete our climactic scene.

Back to the sofa. Bailey sighs, frowns.

"Oh all right", he says. "All right."

I later discover that his life motto is Persistence. I guess my persistence paid off.

John McKay is the writer and director of We'll Take Manhattan.

Comments made by writers on the TV blog are their own opinions and not necessarily those of the BBC.