As supporting evidence I give you http://www.youtube.com/watch?v=TAAyt7-yQ8w (Michael MacKenzie would have made a good Dandy Lord, obviously) and of course http://www.youtube.com/watch?v=RJsaujSs7Fw
It seems so obvious when you think of it, but I don't recall it being mentioned in any official history.
(Fun Rainbow related fact concerning Rod, Jane and Freddy "In June 2008 Rod, Jane and Freddy appeared on the show '50 Ways To Leave Your TV Lover' on Sky and talked about newspaper claims that they were involved in a love triangle. They revealed that Rod and Jane had in fact been married and divorced, Jane partnering up with Freddy some time after he had joined the trio, a relationship that continues to this day." WSMNBTO)