‘Mannstein has designed and built a powerful and robust radio transceiver that is less than a third of the weight of anything we make at IWC. Even with an aerial, a battery and a Morse key or microphone it can be comfortably carried in a leather pouch strapped to your chest. At present there are only a few hand-built prototypes in existence, but if the design could be mass produced it would revolutionise communications.’

Mr Clarke began to sound like his usual self again as he broke into a salesman’s patter. ‘I mean, imagine a radio small and light enough to be carried by every soldier on the battlefield, or every police officer on his beat. Instant communication! Car drivers could radio one another to announce accidents or traffic jams. Some day it’s even possible that husbands could radio their wives in the kitchen to say that they’re on their way home from work.’

‘And that’s what all these documents are, isn’t it?’ Paul said, as he eyed the stack of papers on the seat beside him. ‘Plans for Mannstein’s miniature transceiver.’

‘That’s right,’ Mr Clarke said. ‘You see, in the longer term the compact radio might be a mass-market product, but the Espionage Research Unit is interested in its covert applications. If you’re working as a spy behind enemy lines you need a transceiver that is small, light and tough.

‘As soon as I found out about Mannstein’s miniature set I told my bosses at IWC. They made Mannstein an offer to buy into his company and build a workshop in which to begin producing radios. Unfortunately IWC has been hammered by American imports and we’ve had a few tough years financially. Our offer was far from spectacular and Mannstein rejected it.

‘By this time Henderson had spoken to the British Government about the potential of Mannstein’s design and he was trying to get some money together to up the bid. Unfortunately the whole thing got bogged down in red tape just as the Germans entered the bidding.

‘The Nazis’ attitude is to spend whatever it takes to acquire the best technology available. So while the French Government totally ignored the situation and the British fudged over whether it was right to interfere in the free market, the Germans came in with a gold-plated offer: more money, a brand new factory in Germany and a state of the art research facility where Mannstein could refine his technology.

‘Once the Germans were involved the British upped their bid, but it still wasn’t a patch on the German offer. Mannstein was all set to sign a deal and move his company to Germany, but at the last moment France declared war and the whole thing collapsed.’

‘So he signed the deal with Britain?’