He was a publisher, working for (I think) Secker & Warburg at the time. He was in charge of publicity. They didn't like the fact that a rather uncompromising biography of the twins was being published, and publicised.

It was a bit worrying at the time - he had been approached in a dark alley in Soho (where his office was) - and the police were involved, but as far as I'm aware nothing came of it.