IIRC (and I'm sure I do) a relation of one of the members of The Undertones appeared on Mastermind in the 80's and his specialist subject was the films of Steve McQueen and he got through to the next round where he was thrashed. So I don't think it's dumbed down (recently).

I think I'd do the Flashman books by GMFraser in 1, melodeon players of the 21st centuary in 2, the history of the London Rubber Company in 3, .....