This was the only scurrulous rumour to emerge about John Peel, not much was made of it, no one wanted to tarnish his beloved reputation. Its sad to say it, but in some ways its better that hes died rather than have his legendary reputation tarnished and dragged through the mud. Of course the line has to be drawn somewhere (16 legally /18 morally ?) and im not condoning taking advantage of underage girls for one minute.
I don't think it was a secret - he states in his autobiography that he was fucking very young teenagers while he was in america and that no-one asked to see the birth certificate. Always made it plain that he like schoolgirls, I think there was a big competition he had for 20 years about women sending him photos dressed as schoolgirls.