This was written by Mike D'Abo and Tony Macaulay. D'Abo was lead singer of Manfred Mann, and Macaulay was a successful songwriter who also wrote The Foundations hit "Baby Now That I've Found You" as well as songs by The Hollies, Andy Williams and The New Seekers.
David Essex, who was unknown at the time but went on to success with "Rock On," was offered this song, but he turned it down as he didn't like the title.
This was featured in the 1998 film There's Something About Mary. (thanks, Edward Pearce - Ashford, Kent, England for all above)