If you go to the website with all the data, for NOx in 2017 and 2018 you don't get the big spikes that you get in 2015 and 2016.  I think that's pretty good given the hot weather

https://www.londonair.org.uk/london/asp/advgraphssiteplot.asp?graphtype=Image&site=CT6&period=daily&res=7&day1=1&month1=jan&year1=2015&day2=1&month2=jan&year2=2019&CBXSpecies1=&CBXSpecies2=&CBXSpecies3=&CBXSpecies4=NOXm&CBXSpecies5=&CBXSpecies6=&CBXSpecies7=&CBXSpecies8=&CBXSpecies9=&CBXSpecies10=&CBXSpecies11=&CBXSpecies12=

Looks even more impressive if you look at a chart going back to 2010

thanks

that's pretty clear