The threat the most radical of them pose is evidently far greater at home than abroad: in one characteristically slick and chilling Isis video – entitled “a message to the Jordanian tyrant” – a smiling, long-haired young man in black pats the explosive belt round his waist as he burns his passport and his fellow fighters praise the memory of Zarqawi, who was killed in Iraq in 2006.

‘As in xenophobia?’ said Jack. ‘Or erythrophobia? I know some people really hate my red eyes.’

The dried horseskin was made of brown Canton flannel and was held in place by being thrown over a horizontal stick.

There are habitable planets orbiting many of the stars near our Sun.