Pretty Things, Silk Torpedo, 1974. Photography: A Powell. Hand tinting: R Manning

Thorgerson died in 2013 after a battle with cancer. Powell later described their relationship : ‘We were like brothers ... We were very close, but, in the same way that siblings fight, so did we. Often I had to resort to violence with Storm, if he was trying to intellectually bamboozle me, by throwing heavy objects across the studio at him. But there were always apologies, we always made up ... Sometimes Storm really was so frustrating I had to resort to extreme violence … in the nicest possible way’