In a matter of days, drivers in Camden will face fines if they are caught leaving their engine running while their vehicles are stationary, in a bid to tackle air pollution.
It's not the first borough to do this, others have had the power to penalise idling engines, and in some cases in 15 years only one notice has been issued.
It's lead to other councils calling for futher punishment.
Eleanor Cunningham has the story. Research by Caroline Green.