‘That’s right, sir. I thought I wasn’t mistaken. A bloke in our mess had used those films and I remembered the look of them. Now it seemed pretty funny to me that a man in Markins’ position should be able to afford a Leica camera. They cost anything from twenty-five to a hundred pounds out here when you could get them. Of course, I said to myself, it mightn’t be his. But there was a suit hanging up in the cupboard and in one of the pockets I found a sale docket from a photographic supply firm. Markins had spent five pounds there, and amongst the stuff he’d bought were twelve films for a Leica. I suppose he was afraid he’d run out. I shifted one of his locked cases and it rattled and clinked. I bet it had his developing plant in it. When I left his room I was satisfied I’d hit on something pretty startling. Markins was probably going to photograph everything he could lay his hands on in our workroom and send it on to his principals.’

‘I see,’ said Alleyn. ‘So what did you do?’

‘Told Fabian,’ said Douglas. ‘Right away.’

Alleyn looked at Fabian.

‘Oh, yes. He told me, and we disagreed completely over the whole thing. In fact,’ said Fabian, ‘we had one hell of a flaming row over it, didn’t we, Doug?’

‘There’s no need to exaggerate,’ said Douglas. ‘We merely took up different attitudes.’

‘Wildly different,’ Fabian agreed. ‘You see, Mr Alleyn, my idea, for what it’s worth, was this. Suppose Markins was a dirty dog. If questioned about his nightly prowl he had only to say: (a) That his tummy was upset and he didn’t feel up to going to the downstairs Usual Offices so had visited ours, or (b) That it wasn’t him at all. As for his photographic zeal, if it existed, he might have been given a Leica camera by a grateful employer or saved up his little dimes and dollars and bought one second-hand in America. Every photographic zealot is not a fifth columnist. If he kept his developing stuff locked up it might be because he was innately tidy or because he didn’t trust us, and I must say that with Douglas on the premises he wasn’t far wrong.’

‘So you were for doing nothing about it?’

‘No. I thought we should keep our stuff well stowed away and our eyes open. I suggested that if, on consideration, we thought Markins was a bit dubious, we should report the whole story to the people who are dealing with espionage in this country.’

‘And did you agree with this plan, Grace?’