Gavin like dipping his cock into boy's bums. And Gavin has a really big sausage, and the boys like it. So, as much as I hate using this expression, but it is very illustrative, straight acting (oh, I know hang my head in shame for using it, it is almost homophobic) he'd mix with the straight boys down the pub sculling pots of beer, then be up one of them in the dark in the park on the way home. Heaving like a couple of stallions in the shadows.