“Telephone for Mr Dewsnap.” The voice climbed the staircase in his wake. The door to the Sensitivity Room was closing as Cullis passed, but not before he had glimpsed Sir Richard Croby, a former envoy to the Gabon judged to have gone native.

“Bloody terrible to forget the name of the man you’re having lunch with.”

“Does he have a beard?” Cullis recognised the voice of John Pendock, known to have kept a mistress in Peshawar. Pendock’s appearances had grown rarer since the introduction of computerised telephone calls.

“Better if he did.”

And still the dinning voice. “Mr Dewsnap . . . ”

The PUS walked on, reaching his office at nine-thirty according to the Van Cleef and Arpels clock on his mantelpiece, a gift from the French Foreign Minister.

Yes, in the circumstances the Appointments Board under his guidance had arrived at a correct decision on Wavery. Couldn’t sack a man because he had betrayed his early promise, but one could post the hell out of him.

In welcoming Wavery to his office that morning Cullis made no mention of their encounter at Heathrow.

“Take a seat, Thomas. Yes, there. I want to hear all about Peru.” There followed ten minutes of perfunctory talk while Wavery outlined the political situation after which Cullis said, “I do see you deserve something calmer.”

The PUS spoke with a marked Scottish accent. His pleasures were dry-fly fishing and photographing cemeteries and listening to the shipping forecasts before he slept, normally while reading from a zippered Bible. His reports were admired for their perception and their incision. Whatever humour he possessed found an exclusive outlet in verse. As a young man whose evenings were spent alone in a Lambeth rooming-house he had occupied himself with composing limericks. He had not relinquished the habit in office. A marbled folder in his desk contained several hundreds of verses in what had been described by his late landlady as “a gorgeously light vein”. This trait was not consistent with the rest of Sir Derek’s character. On the few occasions he told a joke, he was terrifying.

Britain’s ability to shift matters on the international stage had diminished during Cullis’ journey up the corridor. Not so his regard for senior diplomats, whom he continued to treat as direct descendants of Homer’s heralds. An ambassador, Cullis believed, was the personification of his embassy. He was not a man in a suit who spoke the language. Quality not quantity was Cullis’ watchword and he harboured a grim dislike for those politicians, with their Rayner scrutinies and Plowden reports, who would wish to retrain his officers as accountants in a global chain store. Cullis, too, was in a pragmatic business. His primary interest was not to make friends, but to defend the interests of the United Kingdom. If the morale of the Service was good, he gave credit to his staff. If it was bad, the fault was his.

This morning there lay on his desk two yellow folders. One contained a post report, including a map of North-West Africa. The other contained Wavery’s career file, to which had been clipped the recommendation made by the Appointments Board at their monthly meeting.