The paper's in-house lawyers have advised me to be less exact about where this took place and with which number bus, lest it jeopardise any proceedings that might be in progress. I would add that I'd imbibed a glass (or two) of particularly excellent champagne over the previous couple of hours, so my testimony might not be as reliable as it should be. But what I witnessed one evening last week was this.

I saw a man – dapper, young to middle-aged, in a well-cut suit, shirt and tie, with an ID of sorts around his neck, suggesting he was in regular employment – being arrested by two large police officers. Before he was handcuffed (quite discreetly, no New York style "perp" walks here), there was a conversation from which it emerged that the arrest was connected with the perfectly normal London bus that was standing empty of passengers at its stop.

Inside were two more police officers and a man who appeared to be the driver. He, the police officers told their captive, had been deeply insulted by what had been said to him and had given a statement. The officers said they quite understood that bus drivers' behaviour could make passengers angry, but that what had been said was an offence. It was not hard to surmise that the alleged remark, or remarks, had been racist. And that what had precipated this outburst had been something that increasingly happens with London buses and is, indeed, infurating.

Suddenly, without apparent rhyme or reason, a recorded announcement says: "The destination of this bus has changed; listen for further announcements". You then find yourself turfed off well before your destination, and probably at a stop where there is no alternative bus or method of transport, and you have no choice but to wait for the next – inevitably overcrowded – service. If you are really unlucky, this can happen twice or even three times on the same route. Unless you know to ask for a "transfer", you have to pay each time.

I should stress that everyone in this little pavement drama conducted themselves in exemplary fashion. The police were polite; they explained what they were doing and why. The man who was arrested was also polite and offered no resistance, nor the slightest trace of bolshiness. As it all wound down, another squad car sped up, and he was whisked off to the police station.

You could say that it says something good about this country and this city that a racist insult against someone just doing his job – let's assume this is what it was about – is treated as seriously as it is. Yet I couldn't help feeling, too, that a full-dress arrest involving at least six police officers, two squad cars and not a little police time, might be a bit excessive. Would an apology, written and in person, plus a donation of, say £100 to the bus drivers' benevolent fund, really not suffice?

DSK's loss could prove the Delors clan's gain

The young French writer Tristane Banon may or may not know it, but in belatedly bringing an attempted rape case against Dominique Strauss-Kahn, over what she says was a particularly nasty encounter in 2002, she could be advancing the cause of women in France in more ways than one. Banon's case, initiated even as the sex charges against the former IMF head threatened to fall apart in New York, means that – for all Strauss-Kahn's denials – he is unlikely to clear his name before the French Socialists have to settle on a candidate for next year's presidential election.

The chief beneficiary of this – aside, of course, from Nicolas Sarkozy who is fully expected to seek re-election – is the current head of the Socialist Party, Martine Aubry. All that had stopped her seeking the nomination before was a year-old pact she had with Strauss-Kahn, agreeing not to stand against him. Last week she threw her hat in the ring – as fate would have it, just before news broke that the case against DSK in New York might be running into trouble. Within hours, Banon's lawyer announced in Paris that he had lodged papers on his client's behalf.

The electoral prospects for Aubry – who, as the daughter of Jacques Delors, strikes fear and dread into the hearts of British Eurosceptics – are by no means hopeless. A serious politician, she has been a highly competent mayor of Lille and pulled the Socialist Party back together after the disappointing and divisive presidential bid of Segolene Royal. It would be poetic justice if DSK's fall indirectly brought France its first female head of state.

My small contribution to the big clean-air society

Among the hazards of any tourist-packed destination, such as London, are the fleets of coaches that drop their wide-eyed passengers off on double-yellow lines, then remain there, noisy and polluting, with their engines on. One day I plucked up the courage to challenge the driver, as the engine of his behemoth rumbled away. "Excuse me," I said, "could you possibly turn the engine off?" He said "No". I said that it was an offence (which it is, punishable with a derisory £20 penalty). He said "No" again and asked what it was to do with me. I said that, as a local resident, I was fed up with the fumes.

So I was pleased to learn that the Mayor, Boris Johnson, was lobbying to have the fine increased to £120. But I was even more pleased when I hit upon what has so far been a sure-fire remedy. Rather than remonstrate with the driver, I went to the front of the bus, took out my notebook and wrote down the number plate. And the company details on the side. Then I took out my phone and made as if to take a photo – which, frankly, I hardly know how to do. By then, though, there was only a vacant stretch of yellow-lined road. I'm not sure whether this would be defined as officious vigilantism or a small contribution to the big society. Either way, it works.