http://nypost.com/2016/10/14/trump-camp-puts-forward-witness-to-refute-sex-assault-claim/
Gilberthorpe made headlines in 2014, when he went public with a claim that as a 17-year-old he procured boys (some who “could have been” underage”) for sex parties with high-ranking British politicians.

Gilberthorpe has no evidence to back up his claim — just his self-described excellent memory.

It's not clear if "his claim" in that last line refers to the 2014 claim or the recent one about Trump.