Those organising events in London might want to advise their delegates that the 50 worst blackspots in the country for illegally polluted air are all in our capital.

The fact was revealed this week after a Freedom of Information request by the London Evening Standard showed that toxicity levels of nitrogen dioxide – a gas linked to asthma, lung infections and other respiratory diseases – were at least twice the legal EU limit at all 50 spots, and up to three and a half times the limit in the worst affected places.

Worst is Marylebone Road which has five illegal blackspots, including notably at the junctions with Glentworth Street and Wyndham Street. Also in the top ten worst are Park Lane, Knightsbridge and the Hammersmith flyover. These are joined at seventh place by Oxford Street, especially at the Orchard Street junction by Selfridges, a fact that was previously dismissed by knowledgeable London mayor Boris Johnson as “b******s” when experts told him last year that the country’s top shopping street harboured some of the worst pollution on the planet.

Also worrying are the increasing levels of particulates, the tiny particles of soot emitted by the diesel engines our government have told us are more environmentally friendly. It is estimated that air pollution kills around 29,000 people every year, and that exhaust fumes increasingly trigger asthma attacks in the UK’s 5,000,000 sufferers.