The start of the UK lockdown brought news of reduced air pollution. Did it last? Measurements from London show that initial improvements in nitrogen dioxide from traffic continued into April and May. Compared with the first 11 weeks of 2020 before lockdown, there was an average decrease of 31% on the capital’s roads. Greatest reductions were in central and inner London and followed improvements from the Ultra-Low Emission Zone. Spring is often the worst season for particle pollution across western Europe. Just six years ago Paris banned half of traffic to control a springtime smog. These are caused by air pollution from traffic and industry mixing with ammonia from farm fertilizer. This year was no different. London had five springtime smogs between the start of UK lockdown and mid-May, but reduced traffic and industry across the UK and Europe meant that maximum concentrations were around two-thirds of those in previous springs. Spring and summer are peak periods for ground level ozone; a pollutant synonymous with Los Angeles smogs. Nowadays, many of the pollutants that cause summer smogs come from solvents, inks and cleaning materials that we use in our homes. Unsurprisingly, the UK had several smog events in the sunny lockdown weather.