‘How do you make them come forward, that’s what I’d like to know! We’ve appealed in the press a couple of times, but all it brought us was an old tabby with a complaint about a conductor. By her account there were six or seven other people waiting, but that’s the beginning and end of her information.’

Gently nodded and drew some patterns on the desk with his finger. This murderer had either been lucky, or else very clever. He had committed his crime in the most improbable of places, and yet, by chance or plan, seemed to have got completely away with it.

‘The buildings bordering the park — was nothing seen or heard from them?’

‘Police HQ, I suppose you mean…! Well, we didn’t, so there you are. From the back here, I daresay, we could have watched from a score of windows — we could have done, but we didn’t. We don’t expect chummies down there!’

‘You’ve got to remember that it was dark,’ added the Super. ‘The car park isn’t lit and the nearest lights are in St Saviour’s. To see anything going on you’d need to put a searchlight on it, and naturally, we don’t spend our nights inspecting the car park with a searchlight.’

‘What about the other buildings?’

‘In effect there’s only the City Hall. The fourth side of the park is bounded by blind ends and derelict property. We questioned the nightwatchman from the City Hall, but it appears that he was doing his pools in the basement.’

Gently was conscious of Stephens leaning forward from behind him. He turned his head. ‘You’ve got a question, Inspector?’

‘Yes, sir — if I may! Perhaps the Chief Inspector can tell me… I was wondering how chummie got the woman into the car park — that is to say, when she was waiting for her bus?’

It wasn’t a question as much as an answer. Put like that, it immediately offered the solution. Gently nodded his satisfaction at his lieutenant’s acuteness, and from the corner of his eye he noticed the youngster colouring up.