Stephen Fry always plays his role to perfection, off-screen and on. At the wedding of the Prince of Wales he looked more regal than the royals. And today he is playing the same avuncular aristo: defending the class system, wishing the Conservatives would revive, chatting about a book he is writing to teach the masses how to write poetry and delivering a few lofty put-downs to Bob Geldof.

Then, just as you are wondering if he is becoming a Wodehousean pastiche, he starts talking movingly about finding the grave of a Jewish ancestor recently desecrated: “It reminded me there really is such a thing as sacrilege.”

While delighting in his Englishness and even his Anglicanism, the revival of anti-semitism has forced him to reflect that he is actually a Jew. He has been warned that he is on a neo-Nazi hit list of British Jews: “They think we deserve to be taught a lesson. The Jews are regarded as clever and they don’t like that. I was told I could have help with fitting panic buttons — Jews look after our own — but I decided against it. Yet the threats are real. Someone like Denis Norden is forever receiving threats. We are still witnessing the smouldering ashes of 50 years ago.”

What is perhaps most shocking is that it shows the intelligence — after a fashion — of these racists. For how many even knew of Fry’s Jewishness until he spoke at a debate earlier this month at the Hay Festival? He recounted discovering that his great-grandfather’s grave in Slovakia had been dug up to extract gold teeth and rings.

Previously, he had mentioned his Jewish ancestry only in his 1997 autobiography Moab is My Washpot, in which he recalled his blood running cold when he read that the young Hitler had been given a longcoat by a Jew strongly resembling his great-grandfather.

Fry is a prominent opponent of plans to outlaw the insulting of religions, notably Islam, but insists that he is motivated by faith in reason, not Judaism: “We all know this is about race. If you embrace Islam, you become an honorary Arab: you take an Arab prophet’s name, you wear Arab clothes. We are kidding ourselves if we say this is about religion.”

Yet the absurd paradox is that the bill would actually make it illegal to criticise the racism of a religion: “You could argue racism is part of Judaism: the unclean people and the gentiles. A good Jew wouldn’t think that but orthodox Jews regard marrying out as dirty and wrinkle at the smell of a goy.”

Fry is formidable intellectually; you could be talking to Roger Scruton. He says of QI, the general knowledge quiz show that he introduces on TV (a new series starts in September): “It is a refuge from popular culture. It is rare, even on BBC2, not to mention a reality show, a soap star or a footballer.”

Is it reinvigorating his faith in television? “We had a question about a Cubozoan box jellyfish with 60 bottoms, four brains and 16 eyes. It is also one of the most venomous animals and brings on nausea and a feeling of impending doom.”

Just like Anne Robinson. “Yes, well, it is certainly like an evening’s television viewing. I don’t watch much. Even Heat magazine has come to see TV as embarrassing.” Er, Fry reads Heat?

“It is in my dressing room. I play a little game of seeing how many pages I can go through before I recognise anyone. There are lots of people called Kelly and Jade until finally you find Charles Dance in the background.”

Does he never ask: “What is a chap like me doing on a show like this?”

“I sort of do but I’m not too embarrassed.” He realises that the BBC commissioned it only because of charter renewal: “It suits the BBC to have shows that can’t be called dumbing down.