It was written by Jerry Corbetta (Keyboardist and Lead singer) and Dave Riordan.
A few versions of the tune have been released, due to the original song being five minutes and fifty-eight seconds long, including long keyboard and guitar solos. The popular version still aired on radio is three minutes and thirty-three seconds long.
Paragon plays the long version, including solos by Mark D and James. Both Mark and Mark carry the "riff", combining bass guitar with low-end Hammond B3 full stop settings.
Here's the original Jerry Corbetta and the more recent iteration of Sugarloaf doing this tune: