ArthurSixpence if you had had sex with the girl from the nightclub then you would have had sex with a minor. You could claim in your defence that you believed her to be 18 because it was a licenced club and she was ordering a beer. If, however, it could be shown that you were aware that the club was frequented by under-age girls then that defence might have been rather less secure.
In Forrest's case he knew the age of his victim. The prosecution were only able to show that the grooming started from when his victim was 14. As posters on the Relationships thread know, adulterers and as in this case abusers, only admit to what they cannot deny. So, is it possible the grooming started earlier?
IMO Forrest has been very conscious of ages, ticking off magic numbers as they were passed. If it could have been shown that the grooming had started earlier then I think that the consequences would have been even more severe for him and he knew it.
However you try to dress it up a 28 year old grooming a 14 year old is a pervert.