To insiders at 10 Downing Street, it was meant to be a harmless joke; a jolly jape that would amuse the Japanese ambassador and his guests. To Lord Mandelson, it was an opportunity to demonstrate his ‘comedy’ side, rarely seen beyond the walls of Whitehall. To the ambassador himself, however, the “coffin stunt” was a personal affront, and one that may seriously damage relations between Great Britain and Japan.

As Lord Mandelson wiped the fake blood from his mouth and creeped sheepishly out of his coffin, a shocked Japanese entourage made their way out of the room, shaking their heads in disgust. “I have never been treated so badly,” said Ambassador Hiro Wakiraysis. “And I was scared out of my pants, too. As was my wife, she did a little pee, it is very embarassing for us and Japanese nation.”

Lord Mandelson claimed to be disappointed with the reaction, with sources close to the Dark Lord saying that he was “bitter, very bitter. He loves a joke, and hardly anyone appreciates that. The coffin stunt was meant to have them rolling in the aisles.”

Home Secretary Alan Johnson said that the prank was “pure comedy”, saying “Mandy and I spent hours on his make-up, as we knew that the Japs love a bit of horror movie and all that. We got this great coffin from the local undertaker, and Mandy lay in there for ages waiting for the delegation to come round on their official visit. Gordon was looking forward to it so much, he kept smiling like a freak – it was hard to keep it from the Japanese.”

“So when Gordon opened the door to the cellar – supposedly to show them his wine collection – there’s this moaning sound and some of the guests looked a little bit freaked out – and then Mandy slides back the coffin lid. Well – we realised then that we might have got it wrong when one of them fainted, two of them ran out, and the Ambassador’s wife left a stain on the carpet. The others just shook their heads. It seems they don’t find this kind of thing funny.”

The evening reception was “frosty” at best, with Lord Mandelson not having removed his dead man’s make-up, and the Japanese guests refusing to eat the Yo! Sushi specials that had been ordered for them.

“It’s a good job we didn’t try the floating eyeball in the soup,” said Mandelson afterwards. “And God alone knows what they’d have made of Gordon’s electric handshake – if it had been working.”