This latest episode in the air pollution debate signifies how politically toxic accusations against the Mayor's air pollution policies have become. Clearly, if you dare to question the Mayor's commitment to the issue you might find yourself on the receiving end of an angry letter and veiled threats...
Whoever takes over from Boris should take heart from de Blasio's victory and be bold. This is not quick-fix politics: it calls for sustained stewardship of our city and its economy. But a brave mayor could lead that conversation, challenge the orthodoxy and change not just London but the national trajectory too.
Given his undoubted charisma and his way with words, he has the potential to be a big vote winner for the Tories. But, and it is in important but, voters who regard humour and a cavalier style as an asset in a city mayor with few real powers might seek different qualities in a national leader. Last week, in an interview with the Sunday Times, he talked about how his six years as mayor had given him the administrative experience that would stand him in good stead in national politics. He has a point. But if he is to be a real vote-winner for his party on the national stage, he needs more. He needs to get serious.
Should Boris win a safe seat, should the Tories win the next election and should Boris be gifted a Cabinet position - the first is the least dangerous of these three assumptions - will Boris commit, even for reasons of his own, to his Cabinet chums and will they commit to him? Boris has work to do. His recent cajoling of Cameron to take a harder-line stance on future negotiations with the EU can legitimately be viewed as the voice of a critical friend. Cameron can take it. However, covert criticism of Osborne, one of the more obvious contenders to succeed Cameron, will endear him neither to the Chancellor nor to others in Cameron's circle of less secure consiglieri.
George Osborne argued yesterday that other cities should have directly elected Mayors with 'clout' like Boris, to drive growth and development outside London. So what is there to learn from Boris and Ken on how to be good Mayors, and what more could their successors in London and their equivalents elsewhere do?
Over the past week the mayor has responded to criticism of his cycling policies by suggesting cyclists are making rash decisions on the roads and by repeating a unfounded claim he made to me in October 2011 that wearing headphones whilst cycling or walking could be blamed for an increase in the numbers injured in London.
Last Friday morning, in the 10 minutes it took for me to get out of the shower, get dressed and head to the kitchen to make breakfast, my bathroom had been engulfed in flames. I was in a rush to leave the house and get to work. If I'd been quicker, I might not have been there when all the lights switched off in the flat.