Although we're still 12 months out from the London Mayoral and Assembly elections, those of us in the large, suburban boroughs that form an outer ring around our city have already been dug in for the best part of a year in what is proving to be a battle of attrition on a key area of contention: the Mayor's plan to extend London's Ultra Low Emission Zone (ULEZ) to include the entirety of the capital.

The judicial review launched in February by a coalition of five councils (the London boroughs of Bexley, Bromley, Harrow and Hillingdon, and Surrey County Council) has now escalated the stand-off to the High Court, with the case expected to be heard in July.