‘Please don’t go. I won’t keep you more than a moment. But I must tell you I’m terribly interested in the Moore case. I can’t help wondering if you knew him, you’re here so much.’

‘I knew him,’ said Mrs Jones distantly.

‘That’s terribly exciting.’ And the woman did look very excited. ‘I suppose you first met him when he came into the shop?’

‘That’s right,’ said Mrs Jones and she got up. ‘But I don’t care to talk about it. It’s a very long time ago and it’s best forgotten. Good morning.’

‘Oh, but please . . .!’

Mrs Jones ignored her. She walked far more rapidly than usual, breathing heavily, along the path towards the old town. She was flustered and upset and very put out. To rake up all that now just when she was thinking of the lovely events of that time! For that day, though not, she hoped, for the future, the encounter had spoiled the seat for her.

‘Had a good day with Cottle?’ said Hugh.

‘Don’t speak to me about that man. Can you imagine it, I gave him a ring and a woman answered! She turned out to be some creature on holiday like us who was taking him to Lowestoft in her car. I could come too if I liked. No, thank you very much, I said. What about my finding the girl called Jones? I said. And he was pleased to tell me I was getting obsessional. So I gave him a piece of my mind, and that’s the last of Arnold Cottle.’

And the last of his ten pounds, thought Hugh. ‘So you went on the beach instead?’

‘I did not. While you were out in that boat I researched on my own. And most successfully, I may add. You remember that old man in Clacton, the one in the old folks’ home? Well, he was quite fit enough to see me today, and I questioned him exhaustively.’

Hugh said nothing. He could guess which of them had been exhausted.

‘Ultimately,’ said Cecily, ‘I was able to prod him into remembering. I asked him to try and recall everyone he had ever known called Jones. And at last he remembered a local policeman, Constable Jones, who got married in or around 1930. And the girl he married worked in a local chemist’s shop. How about that?’

‘You mean she was Moore’s girlfriend?’

‘Isn’t it obvious? Her name was Gladys Palmer. She is now Mrs Jones. Moore was seen about with a girl in Clacton. This girl lived in Clacton and worked in a Clacton chemist’s shop. Now it’s quite evident that Moore was having a love affair with Gladys Palmer and that he persuaded her to give him the cyanide from the shop where she worked. The real evidence is that, according to all the books, that was one of the few chemist’s shops from which Moore never tried to obtain cyanide!’

‘That’s real evidence?’ said Hugh.

‘Of course it is, to anyone with any deductive powers. Gladys Palmer took fright when Moore was found guilty, so she married a policeman for protection, and the policeman’s name was Jones. Isn’t that proof?’