Callum Jardine was practised in the art of looking relaxed when he was not — much more so, he observed, than those keeping an eye on his movements. The two men who had tailed him from the Marconi Wireless office, almost caricature Frenchmen in their berets, striped jerseys and too-clean blue overalls, were now sitting a few tables away, making a poor fist of their supposedly disinterested surveillance.

Their attempt to look like working men was risible; worse, they were fidgeting, acting as though he was about to get up any second, dash to the edge of the quay, jump into a boat and vanish, when in fact he was quite content, given he had nothing to do for several hours, to keep them in this cafe while he read his newspaper and consumed his petit dejeuner.

When not idly scanning the news he could watch the last of the fishing boats enter the harbour of La Rochelle to unload their overnight catch, which made it pleasant to sit and while away time on a fine late August morning, already warm and getting warmer, and to idly speculate about the history of a part of France he had never previously visited.

In a country where governments came and went with tedious regularity, in which politics and politicians seemed to operate on a revolving door, the same faces reappearing in various ministerial disguises, and one much given to strikes by dissatisfied workers, La Rochelle had an air of tranquillity belonging to a port and city that had been rich for millennia, a sort of bastion of a more conservative France.

The harbour reflected this longevity, dominated as it was by three medieval towers; they formed as well as narrowed the entrance to the inner anchorage, which made it easy to imagine how the locals had come by their wealth, with, over a millennium, ancient galleys and sailing ships needing to pass through that gap and pay for the privilege, an entry point for goods from all over the world, including at one time, highly profitable African slaves.