Drivers of diesel cars are being hit with an extra £2.45 charge to park in parts of central London.
In a push to tackle toxic air pollution, Westminster council launched a trial of the “D-charge” in the areas of Hyde Park, Marylebone and parts of Fitzrovia.
It is the first UK town hall in Britain to impose an extra charge on parking bays.
The move comes amid a raft of new measures to cut air pollution, including air marshalls tacking drivers of large vehicles who leave engines running while doing deliveries.
The charge per hour for all pre-2015 diesel vehicles will be £7.35.
Other vehicles will continue to be charged £4.90 per hour.
The 50% extra charge is intended to deter the heaviest polluting vehicles from parking in the area.
It has the backing of community groups including the Marylebone Association.
In October, Sadiq Khan is introducing a £10 “T-charge” for older, more polluting cars, on top of the congestion charge.