"What is the probability of an imposter?"

You should still evaluate for yourself.

However, the email acct used to register was that of the attendee and presenter at the Cambridge conference Classifying Sex: Debating DSM-5 who was vilified by The Telegraph et al.

As he wishes to post as himself, and as his university e-mail is a matter of public record, I feel no bones about stating the reasons I'm confident that its him.