We were told to arrive by 8.15am as, after that, Downing Street would be in “lockdown” for Senator John McCain’s visit. I am not sure when Downing Street adopted the language of Die Hard but it seemed appropriate for an all-American action-man politician.

The lights were on for, of course, the Prime Minister had been up since 5am. Outside, rain threatened and seagulls, apparently lost, screamed overhead. Spring has not quite yet sprung: the tulips were struggling to open but, in the hanging baskets, the eyes of pansies faced towards the heavy black door. It was the shiny old door that the presidential candidate Mr McCain cared about. He wanted to be photographed going in and out, near it, around it. That door could make him look like an international man of mystery, a statesman, a heavyweight.

The choreography of the visit was a nightmare. This summer, Mr McCain will become the official Republican candidate. In November, he may become the most powerful man in the world. But for the moment, he’s just a senator who was visiting with his “co-del team”, short for congressional delegation. The rules of protocol do not bend for the delicious possibilities of tomorrow. Mr McCain would be given no red carpet, no doorstep greeting.

The first Americans arrived in a large white minibus, a sort of political Humvee. This held the “co-del”, who disembarked and stood on the pavement. A BMW with Mr McCain purred up: the candidate emerged and, bizarrely, shook hands with his own co-del. Protocol is a cruel mistress when it means that an ambitious man has to arrange his own welcome party.

The Door opened — controlled by an invisible hand — and 11 people trooped in. Five cars parked up. Inside, Mr Brown and the co-del sat in the Cabinet Room and talked of war (the co-del had just been in Iraq and Israel). Photographers were allowed in to record the official handshake moment. By all accounts, the small talk was positively microscopic.

After about 45 minutes of this, the Door opened. We saw a forbidden glimpse of Mr Brown and Mr McCain having one or two action-man handshakes. Then the Prime Minister peeled off and the co-del came out alone, striding towards the microphones. Mr McCain speaks so softly that we had to crawl forward, knees on tarmac, to hear. The voice is extraordinary: soft, measured, authoritative, grandfatherly. He must have had this voice his whole life but it’s hard to imagine on a young man. Now, at 71, it fits his face, as square as patchwork.

He was wearing tasselled loafers and clutching a gobstopper of a book, The History of the Twentieth Century by Sir Martin Gilbert. Apparently Sir Martin had been to see Mr Brown the day before and dropped it off. “I have already read it,” he noted.

If the voice lulls, the words do not. He is, as the Americans say, a straight-talker. Pro-war, revolutionary on climate change, adamant on Tibet. He’s a fan of Mr Brown. He was asked about a comment he had made about Iran that was incorrect. “We all misspeak from time to time,” he said. “So we’ll just move on.”

And so they did. As they left, a man staggered up Downing Street with a roll of red carpet. The King of Bahrain was on his way.

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