Who was the original presenter of the British TV show "Mastermind"?

He also was happy for his contact details to be public so that anyone could contact him about the answer to a tricky question (maybe something in a pub quiz game).

I enjoyed Mastermind and I was thrilled when I managed to get a question right on the general knowledge section. The questions were genuinely hard, especially the specialist ones. I was happy to discover that the black leather chair was presented to Magnus when the show finally went off the air.