Joseph Ratzinger, originally from Munich but now living in Italy, wrote to the Queen last year asking if he could pop in on his way to meeting Susan Boyle in the middle of a park in Glasgow.
Her Majesty agreed to his request despite concerns over his involvement in covering up paedophilia and his quirky belief that being gay is worse than raping a child.
Experts have also stressed that Mr Ratzinger's claim that everything he says is infallible means that instead of swapping gently amusing anecdotes with the Queen and being driven about in a bullet-proof ice cream van, he should really be in a secure, windowless room and injected every half hour with a thunderous dose of temazepam.
Criminal psychologist, Dr Julian Cook, said: "Britain's mental hospitals are full of people like this. Old, confused, fascist perverts who think Jesus has set up camp in their sock drawer.
"If we have any compassion we will try to trap Mr Ratzinger using a large net, or perhaps a hole covered in twigs and leaves, and then give him the 24-hour care he so desperately needs."
Tom Logan, visiting professor of visits at Reading University, said: "The Queen has met some splendidly nasty fruitcakes in recent years. I'm thinking particularly of that rotund Saudi gentleman who thinks women are pack animals and that you should chop someone's hands off if they steal a packet of Toffos.
"But at least that was underpinned by a lovely big arms deal. If only Mr Ratzinger would order a couple of dozen Eurofighters and a class 2 destroyer we could coat this whole mucky business with a nice, hard-headed rationale."
But Mr Ratzinger's arrival was overshadowed last night after one of his best friends described Britain as both a 'third world country' and a society with a frighteningly high number of people who can read and think.
Logan added: "When I heard the phrase 'third world', I didn't think he was being racist or particularly offensive, I just assumed he must have driven on a British motorway.
"So yes, in that sense Britain is like a third world country, the key difference being that thousands of people aren't dying of AIDS every day because some mad old fucker in a pointy hat told them that johnny bags are made by Lucifer."