The Queen was born on Wednesday April 21, 1926 in the family town house at 17 Bruton Street in Mayfair, central London. I was born on Wednesday May 12, 1926 in a nursing home at 323 St Margaret’s Road in Twickenham, west London. She arrived 12 days before the general strike; I was born the day it ended.

Britain has changed almost beyond recognition since. Then, a fifth of the world in our school atlases was coloured red to show the unsleeping boundaries of the British empire. We were still not quite a full democracy: women under 30 did not get the vote until 1928. Homosexuals were outside the law, abortion was the province of the rich, the pill was undiscovered. We still hanged and flogged fellow human beings.

Television and space flight belonged to science fiction. Computers were unknown and the word teenager had not entered the language. Once the coldest race in Europe, we now have some claim to be among the randiest races on earth. The Queen has, by definition, been at the epicentre of all these volcanic changes and has never looked even slightly surprised by them, let alone rattled.

Looking from 2006 it’s hard to realise now just how close the threat of red revolution seemed to those who worked the levers of power back then. An Oxford undergraduate and former officer was asked in the 1920s to leave Balliol, of all places, because he had spent his vacation in Russia.

Yet 1926 is the last year in which a clear class struggle was fought here. The island race relaxed after the general strike. The most characteristic sound of the 1920s from then on was not the Red Flag but the charleston. It was the era of cads and cocktails, the bottle party and the shimmy. Noël Coward and Somerset Maugham had four plays apiece running in the West End. The future Queen’s theatre-loving mother was seen at a play a week before she was born; mine went to see the matinée heart-throb Godfrey Tearle and fell for him so hopelessly that she lumbered me for life with his first name.

After that our paths diverged. The Smiths of Surbiton and the Windsors of Windsor did not mix much socially. Yet we lived in the same aspic and shared the same national experiences.

My father, who always stood to attention when the national anthem was played on the wireless, brought home the Daily Mail on January 21, 1936 with its front-page picture of the dead George V and said, in a rare show of emotion, “George the beloved”. On December 11 of that same year we sat around the fire listening on the wireless to Edward VIII talking to us about his abdication. My father said nothing, but I think Edward’s abysmal witterings planted in me a mild republicanism which persists to this day.

For example, I now think that when his time comes Charles should renounce the crown but continue as prince on his messianic mission to restore us to a smiling land sustained on organic cakes and real ale.

Our draughty little province of Europe looks increasingly Ruritanian as a kingdom. Still, I raised my glass to Elizabeth on November 20, 1947 on our fly-blown RAF base by the Suez Canal when she married Lieutenant Philip Mountbatten RN. I raised another one (or two) in the suitably Brideshead setting of Tom Quad at Christ Church, Oxford, on the night of November 14, 1948 when she gave birth to Charles, her eldest son and heir.

It was not until 1964, 12 years into her reign, that our paths properly crossed again. The Queen was due in Quebec and since John F Kennedy had been murdered the year before, there was genuine concern that French-Canadian extremists might carry out their threat to kill her.

I happened to be in New York for this paper and was ordered to fly to Quebec at once to cover the story. So intense was the hysteria that it was not at all clear, even the night before, whether the Queen would arrive at all or whether her security advisers would abort the trip.

I was staying at the Chateau Frontenac hotel, with a majestic view of the St Lawrence causeway down below, and got up early the next morning to see for myself. From my bedroom window I saw an armada of small ships sailing up the St Lawrence towards me. In the middle of them was the royal yacht Britannia, dressed overall, its pennants fluttering in the breeze. The Queen’s answer to the terrorists was perfectly clear. She was going to do her job as she had promised.

It would be difficult to disentangle my emotions as I looked down on that magnificent royal statement of intent, but republican they were not. There was of course, in the upshot, no attempt on her life but there was one small hitch. The Queen was due to pay an official visit to a Canadian naval vessel in the harbour and I was on the quayside as she arrived for it. But she stopped just as she was about to go on board.