Angela Merkel, the Chancellor of Germany, is complaining to the US about the alleged tapping of her mobile phone. Mrs Merkel feels that she must protest for the sake of domestic public opinion – just as François Hollande, the French president, did earlier this week about the National Security Agency’s acquisition of French telephone records – but she cannot pretend to be surprised that the capability to monitor her phone calls exists, because she will have authorised similar operations herself.

The unpalatable truth is that eavesdropping is as old as any occupation. The term sub rosa comes from the flower placed over the door of the Roman senate to indicate to outsiders that the members were in secret session. Espionage became a growth industry in the Elizabethan era when Sir Francis Walsingham was credited with obtaining the evidence, by clandestine means, that condemned Mary Queen of Scots to her execution.

During the First World War the interception and decryption of the notorious Zimmermann telegram, which exposed the Kaiser’s scheme to persuade Mexico to join the Central Powers and attack the United States, led Woodrow Wilson to declare war on Germany….

The French GCR, the Swedish FRA, the Dutch AVI, the Norwegian SIGINT agency at Saeter and, yes, the German BND, Angela Merkel’s own foreign intelligence agency, all toil in the same vineyards, hoping to assemble an electronic haystack of metadata – that is, the time, duration and location information required for telephone billing purposes, in which the tell-tale needles may be traced.