“Will it make any difference?” asked Giles. “Whoever gets the job will still be phoning reverse charges to Moscow before he can take any decisions.”

“While the foreign secretary,” the civil servant continued, ignoring the remark, “is keen for you to discover if this would be a good time for the UK to make another application to join the EEC.”

“Has De Gaulle died when I wasn’t looking?”

“No, but his influence has waned since his retirement last year, and Pompidou might feel the time has come to flex his muscles.”

The two men spent the rest of the flight going over the official agenda, and what HMG hoped to get out of the conference: a nudge here, a wink there, whenever an understanding had been reached.

When the plane taxied to a halt at Berlin’s Tegel airport, the British ambassador was waiting for them at the bottom of the steps. With the help of a police escort, the Rolls-Royce whisked them across West Berlin, but came to an abrupt halt when it reached Checkpoint Charlie, as the Western Allies had dubbed the wall’s best-known crossing point.

Giles looked up at the ugly, graffiti-covered wall, crowned with barbed wire. The Berlin Wall had been raised in 1961, virtually overnight, to stop the flood of people who were emigrating from East to West. East Berlin was now one giant prison, which wasn’t much of an advertisement for Communism. If it had really been the utopia the Communists claimed, thought Giles, it would have been the West Germans who would have had to build a wall to prevent their unhappy citizens from escaping to the East.

“If I had a pickax…” he said.

“I would have to stop you,” said the ambassador. “Unless of course you wanted to cause a diplomatic incident.”

“It would take more than a diplomatic incident to stop my brother-in-law fighting for what he believes in,” said Giles.

Once their passports had been checked, they were able to leave the Western sector, which allowed the driver to advance another couple of hundred yards before coming to a halt in no-man’s-land. Giles looked up at the armed guards in their turrets, staring down grim-faced at their British guests.

They remained parked between the two borders, while the Rolls-Royce was checked from the front bumper to the boot, as if it were a Sherman tank, before they were eventually permitted to enter East Berlin. But without the assistance of a police escort, it took them another hour before they reached their hotel on the other side of the city.

Once they had checked in and been handed their keys, the golden rule was for the minister to swap rooms with his permanent secretary so he wouldn’t be troubled by call girls, or have to watch every word he said because his room would certainly be bugged. But the Stasi had caught on to that ruse and now simply bugged both rooms.