From Gear Guide (Hip Pocket Guide to London's Swinging Fashion Scene) published in London in May 1967.
Bill 'Vince' Green was a stage portrait photographer who specialised in taking shots of body-builders. One of his problems was finding briefs that were brief enough and close fitting to show off the body beautiful to the best effect. There seemed to be no solution to his problem until Vince started making the briefs himself. He tried using stretch material intended for women's roll -ons and other unlikely cloths. it was really only a part time activity for Vince, but his name spread - people started turning up and asking for briefs to order in unusual materials. Even visiting royalty sought him out and were fitted with swimwear. In 1954 he visited Paris and was struck by the clothes of the beat Left Bank student fraternity and cafe society - young people who lived it up through the night in the cafes wearing dark glasses and a lot of denim.
Denim took Vince Green's fancy. He discovered that people were actually bleaching their denims and sitting in baths to shrink them to body-hugging shapes. It seemed a great idea and Vince decided to sell denim made like this. In October 1954 he opened up a boutique selling pre-shrunk pre-bleached clothes. At the beginning the trade was highly amused and though it a quickly passing gimmick. But soon he was supplying his denim wholesale to big stores like Harrods. Today over a decade later, this particular gear style is still very popular in many different forms. Is not surprising and new as Vince probably thought. In the days of the great army of the Russian Czar's the officers were known to sit in the hot baths to soak their sealskin trousers before a big parade or ball.
Vince's was probably the first boutique. It was quickly known to the new money earning young who where prepared to spend plenty of their earnings on looking good. Enough of them went to his place to ensure the success of his new venture.
But it was the next move the probably had the greatest effect on really getting the gear seen moving. An assistant to Vince – John Stephen – moved away and worked in a number of other small clothes shops specialising in new clothes in the Notting Hill and Baker Street district of London. These new little shops, bright, gay and intimate (unlike the traditional big clothes store or specialised shirt or men's shop) proved to be very successful. Stephen decided to set up on his own. He came back to Soho, the area where Vince had started, and opened a one room boutique on a second floor in Beak Street [after a disastrous fire at this shop his sympathetic landlord offered him a store round the corner in Carnaby Street, until then a row of dowdy shops,-- the rest is history…]
More info at A Dandy in Aspic (thanks for pic)