When my editor called on Friday and said: “We want you to write about your brother”, I allowed her to hear my groan, just to remind her that we are a person in our own right.

Only an hour earlier I’d also rolled my eyes when the presenter of Woman’s Hour cued me in as an author and columnist “whose brother Boris dabbles in local politics from time to time”. Goodness me, I’d thought wearily, this was the sort of sexist thing one might expect from an unreconstructed male on TalkSport, yes, but not from the serious Sunday newspapers or the Daily Cervix.

Still, as the Conservative surge and an energetic campaign have swept my brother to power, I can’t claim to be surprised. The power blond has become mayor of London, bringing another act in his spectacular and entertaining career to a glorious ending, and I . . . am his sister.

And to be honest, for weeks, months, years, actually for decades, people have wanted me to talk about Boris. When they see me, they think of him (something to do with our yellow hair and big noses, I think) and the one thing they know for a certainty is that my sole purpose on this earth is to furnish them with a brief opportunity to stand in the presence of his blood. And, boy, do they like to make the most of it. In order to make this more amusing (much as prisoners whittle in solitary confinement) I play a little game.

When someone I don’t know rushes up to me, looking thrilled, I never make the mistake of believing they are pleased to meet me or have read something I’ve written. No, I put on my care-in-the-community smile and silently start counting. As they say: “Ooooh it’s so lovely to meet you, what fun. Now listen . . . ”, I’m going: “One, two, three, four . . . ”, and before I hit five, the person tells me they are a huge Boris fan and beseeches me to deliver, in person, a complicated message to do with something vitally important such as the location of a bus shelter in Old Bexley & Sidcup.

So – Boris. It’s all anyone wants to hear me talk about. I have your total attention for once. And, finally, a subject I know a tiny bit about. Which makes it all the harder, strangely. So I telephoned him.

“I’ve got to write about you. What shall I say? I want to write about how you’re going to make London light and fun again, and stop people from feeling like cogs in a totalitarian machine designed by Transport for Lefties, but I don’t want to emphasise your jokes, and I want to say that far from disappointing people, you will exceed their expectations,” I said.

“A lot of people knew they were taking a slight risk when they voted for me,” he said, “but what I want them to know is that when Peter Oborne called me ‘chillingly efficient’, he was scratching the surface. If elected, I will exhibit a Prussian attention to detail.” “Great – that’ll do,” I said, and left him to write his two speeches.

Actually, there’s more. I may be partial but nobody could have observed the Boris campaign and doubted his commitment to the job. The effort it took him not to be funny, and to stick to the same old dull script without deviation or hesitation, and with endless repetitions, was superhuman. He never stopped.

I know this sounds awfully Oprah but it really was quite moving at times to campaign for him (cabbies to a man all wanted to shake my hand) and to play my part in Ken’s downfall. In the Holborn call centre (smile and dial, we were told; smile and dial) where I was cold-calling the less plush outlying boroughs, I found people to be warm and receptive and braced for Boris, and when I drove around the streets with a megaphone late on Thursday, before the polls closed, shouting, “Vote Boris”, and so on, which was noisy and annoying for everyone, people gazed on indulgently and gave the thumbs-up.

And I should confess – it was also refreshing to encounter those who hadn’t drunk the Kool-Aid yet, or who were congenitally incapable of voting for a Tory, even a nice one. I became adept at spotting people who wouldn’t vote for him but didn’t want me to know. They’d slide away from me in lifts, or fail to meet my eye, as if I would be offended by the fact that they were Labour or Green, which was nuts – frankly, campaigning offered me a rare opportunity finally to encounter people who didn’t within five seconds declare themselves to me as avid Borisophiles.

One rainy morning last week I was on the stump in Kensington & Chelsea, where getting out the vote for a Tory would, you would think, be like shelling peas. I’d forgotten that in a true-blue borough such as K&C lots of residents are so rich, they can afford to vote Labour.

So there I am, in a posh street in Notting Hill, knocking up. I ring a bell, a voice comes over the intercom and I launch into my spiel.

“Sorry to interrupt; I’m canvassing on behalf of Boris Johnson, and we just wondered whether we can rely on your vote,” I oozed.

“No, thanks – that’s none of your business,” the voice crackled. “Oh. Can I ask then how you voted in the last mayoral election?” I persisted. The voice turned ratty. “You heard me! None of your business!”

“Well, I think you can put Mrs Crabby down as a no,” I said loudly. I left the doorstep, looked up and saw Philippa Walker, aka Mrs Alan Yentob, at a computer.

At that moment a Mercedes pulled up. A tall woman with short, dark hair, swathed in fox fur, unfurled herself, followed by two dogs. Forgetting Mrs Yentob, I chased after her. “Can I give you a Boris poster to put in your window?” I asked, suddenly realising it was Lucy Ferry, mother of Otis, former wife of Bryan.

“No,” she snapped, taking out keys to let herself into a £5m house, and tossing her head. “I’m a communist.” Which is fine. In fact, it is now irrelevant. The die is cast, or, as Boris likes to say, alea jacta est. So for all those who did vote for him, and indeed all those who didn’t vote for him, here’s my tuppence ha’penny.

Boris is incorruptible. He works harder than anyone I’ve ever met. He is funny and modest (even though he used to tell me that he had forgotten more Latin and Greek than I would ever know). He is generous, ambitious, competitive, greedy, devoted to his family, lacking in vanity, uninterested in celebrity, glamour and social status and 100% committed to doing his best for London and all Londoners.

I am incredibly proud of him.

rachel.johnson@sunday-times.co.uk

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