Founding member Francis Bacon joined the day after opening, and he and Belcher formed an unbreakable bond — she "mother," he her adopted "daughter." She paid him a weekly retainer plus free drinks to bring in wealthy friends, and the club became a staple for British artists, its circle included George Melly, Jeffrey Bernard, Frank Auerbach, Peter Blake, Henri Cartier-Bresson, Alberto Giacometti and Lucian Freud. 

Under former barman Ian Board (1979–94) and later under Michael Wojas (1994–2008), it became a magnet for the Young British Artists — Damien Hirst, Tracey Emin, Sarah Lucas (who also worked shifts behind the bar) and Sam Taylor-Wood.  Wojas even had celebrity members like Kate Moss serve drinks as a promotional stunt.

The Colony's art legacy runs deep: Michael Andrews' 1962 painting The Colony Room captured the scene inside, including Freud and Bacon; Bacon painted several portraits of Belcher, one selling at auction for £13.7 million; and a Damien Hirst spot painting once hung above the bar alongside a Sarah Lucas self-portrait made of twisted cigarettes.

What made the tiny room so magnetic was more than the history or the art — it was the freedom within its walls. As Bacon put it, "you drop your inhibitions at the entrance." 

The Museum of London later summed up Belcher's gift saying she created an ambiance suited to those who saw themselves as misfits or outsiders, describing her as an "imperious lesbian with a fondness for insulting banter," 

George Melly called her “a benevolent witch, who managed to draw in all London's talent up those filthy stairs. She was like a great cook, working with the ingredients of people and drink”.

Belcher ran the room until her death in 1979; the club carried on without her until finally closing in 2008 — one of the last truly unruly outposts of bohemian Soho.