Finishing off Obama's joke

He kicked off his speech yesterday with this:

I have known few greater honors than the opportunity to address the Mother of Parliaments at Westminster Hall. I’m told the last three speakers here have been The Pope, Her Majesty the Queen, and Nelson Mandela, which is either a very high bar or the beginning of a very funny joke...

He got a good bit of laughter for that. It's probably because everybody in the audience knew the old joke about political correctness at the BBC and realised that Obama had just admitted he was gay.
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The old joke about political correctness at the BBC is of course highly offensive and I repeat it here for research purposes only and not because I think it's funny or anything:

A new scriptwriter for a comedy show is told that there are certain things he can't make jokes about: religion, the Royal Family, infirmity/disability, race or homosexuality.

"That's a long list, " replied the scriptwriter "How am I supposed to remember all that?"

"We have a mnemonic of sorts," replies the old hand "It goes like this: 'Oh my G-d!' said The Queen 'I do believe that one-armed n-gger is a poof'."