Absolutely correct, my mistake.
Not being a fan of the sequel at all I had to look on IMDB for the culprit behind this terrible fuck up of a sequel, i saw gregory as the writer but at a glance failed to notice that his writing credit only stretches as far as (Characters). So of course his name pops up on 2, 3, Endgame and the 5th, the source.
The real culprits are Peter Bellwood, William Panzer and finally Brian Clemens, whos IMDB listing reads like Troy McClure's biography. "Hi i'm Brian Clemens, you may remember me for writing such tv shows as 'Nurse will make it better' and 'Won't write home mum, i'm dead' (actual listings)
Russell Mulcahy and Peter Bellwood however, being involved in the first have no excuse, paycheque or not.