Brian Clemens, creator of The Professionals, said Collins brought a "Bond-ian quality" to the role of Bodie.
"I thought he would have made a marvellous Bond," he told the BBC. "He was tough and he could fight, he looked good, he was handsome and he had this nice sense of humour.
"I knew he had auditioned [for James Bond] and I think they were wrong not to take him up."
Mr Clemens recalled Collins also undertook a lot of physical training for the role of Bodie.
"He took up parachute jumping soon after joining The Professionals. It was the sort of thing you would expect a Marine to indulge in. He was a method actor in a sense."