‘They are not gods,’ the General stressed. ‘Uneducated, barbaric peasants centuries ago might have thought them gods when the Tuatha De Danann first ventured here, but we’re above such primitive nonsense. Yes, they have immense power. Yes, they can do things beyond our current understanding. But they are not gods. And they can be defeated. We have to use our intelligence, our resilience and the other abilities given to us by Himself. The real God?’

Manning sipped her drink quietly, but Hal could tell that she was not convinced.

The General turned to Kirkham. ‘Review what we know.’

‘Einstein postulated the idea of a parallel universe… other dimensions. Of course, they’ve always existed in myth. The home of the gods. Asgard. Avalon. Now we know, in this as in so many other ways, that the old stories have a greater degree of truth in them than we suspected. But the roots are also there in solid science-’

‘You’re not about to go off on one of your interminable incomprehensible rambles, are you?’ Reid said wearily. The General waved him quiet.

Kirkham was unperturbed by the interruption. ‘It all comes down to String Theory. Complicated physics, I know, but bear with me. In nineteen ninety-five, Edward Witten at the Princeton Institute for Advanced Study came up with what he called M-Theory, which implies the existence of higher dimensional shapes called membranes, or branes for short.’ Kirkham, as always, was not about to be rushed — or deterred. ‘Branes can be as large as a universe. Indeed, a brane might even be a universe, and we could be living in one right now.’

‘And the point is?’ Reid enquired rudely.

‘The point is that reality is not as clear cut as we were taught growing up. Witten described string theory as “twenty-first-century physics that fell by chance into the twentieth century”. We’re at the cutting edge of science here. Is the Otherworld of Celtic mythology another brane? Are the gods the inhabitants of that brane, as we are of this one? Is it possible to leak between the two in the same way that M-Theory suggests happens to excess gravity strength?’