The pictures for the poster were taken in a London hotel bathroom in 1967 (Robert Davidson)

THEY are some of the most iconic images from the late 1960s, adorning posters, T-shirts and mugs for 50 years. Yet the man who took the photographs of the American musician Frank Zappa sitting on a lavatory has hardly made a penny from them.

Robert Davidson took a dozen pictures of Zappa in the bathroom of a central London hotel in 1967 to illustrate a newspaper article. Three months later, he claims, men sent by Herb Cohen, Zappa’s manager, arrived at his study in Soho and demanded he hand over the negatives.

“I had little alternative as they were threatening,” said Davidson, who photographed an array of bands during the 1960s, including the Rolling Stones and the Moody Blues.

For almost five decades, Davidson watched