He was about one-eighty in height — that’s six foot in old money — and dressed in a beautifully tailored suit that emphasised the width of his shoulders and a trim waist. I thought early forties with long, finely boned features and brown hair cut into an old-fashioned side parting. It was hard to tell in the sodium light but I thought his eyes were grey. He carried a silver-topped cane and I knew without looking that his shoes were handmade. All he needed was a slightly ethnic younger boyfriend and I’d have had to call the cliché police.

When he strolled over to talk to me I thought he might be looking for that slightly ethnic boyfriend after all.

‘Hello,’ he said. He had a proper RP accent, like an English villain in a Hollywood movie. ‘What are you up to?’

I thought I’d try the truth. ‘I’m ghost-hunting,’ I said.

‘Interesting,’ he said. ‘Any particular ghost?’

‘Nicholas Wallpenny,’ I said.

‘What’s your name and address?’ he asked.

No Londoner ever answers that question unchallenged. ‘I beg your pardon?’

He reached into his jacket and pulled out his wallet. ‘Detective Chief Inspector Thomas Nightingale,’ he said, and showed me his warrant card.

‘Constable Peter Grant,’ I said.

‘Out of Charing Cross nick?’

‘Yes sir.’

He gave me a strange smile.

‘Carry on, Constable,’ he said, and went strolling back up James Street.

So there I was, having just told a senior Detective Chief Inspector that I was hunting ghosts, which, if he believed me, meant he thought I was bonkers, or if he didn’t believe me meant he thought I was cottaging and looking to perpetrate an obscene act contrary to public order.

And the ghost that I was looking for had failed to make an appearance.