‘He knew about the Rivers,’ I said. ‘He must have thought it would be handy to have a way of keeping them under surveillance.’ Or perhaps he’d known that sooner or later he was going to have to go mano a dios with Lady Ty.

‘Still not a bad little investment over five years I suppose,’ said Stephanopoulos. ‘But why a sniper? It’s not his MO.’

‘If he wanted Olivia dead he knew he’d have to go through her mother first,’ I said. ‘And he knew he had to take Tyburn down before she was aware of the attack. Otherwise Lady Ty, this close to her river, this close to the Thames – not going to happen.’ I looked across at the blinded window opposite.

‘He can’t possibly have missed at this range,’ I said.

‘And yet he’s the one who’s dead,’ said Stephanopoulos. ‘Could she have thrown a sword across that distance?’

I tried to imagine Tyburn pivoting smartly on her heel, bringing her arm back and flinging a sword across the gap between the houses like a bad special effect. The sniper staggering back, looking down in amazement as half the blade and the pommel vibrate amusingly in his chest. Not enough style points for Tyburn. And anyway, they never found the sword.

‘If she threw it,’ I said, ‘then who pulled it out?’

Stephanopoulos gave the traditional short sigh of the senior officer who is about to explain something they thought was bleeding obvious right from the start of the conversation, but obviously wasn’t.

‘No offence, Peter,’ she said. ‘But we were kind of relying on you to provide that information. Us just being normal run of the mill coppers none of who are versed in the mystic arts or currently shagging a supernatural creature.’

‘That you know of, Boss,’ I said, thinking of Wanda the manageress, who you wouldn’t spot as ‘special’ if you didn’t know what to look for. But Stephanopoulos was right. This was the Folly’s area of expertise, and it was embarrassing that we were so bloody crap at it.

Assume for the moment that the dead sniper had something to do with laughing Sir Tyburn – thought dead by his father and brothers these last hundred and fifty years.

But we know that apparent remnants of normal human beings can be left behind, and under particular circumstances can physically interact with the mundane world.

Do gods have ghosts? I wondered.