Five councils have lost their High Court challenge against the expansion of London’s ultra low emission zone (Ulez).

Here, the PA news agency answers 12 key questions about the scheme and what happens next.

– When and why was the Ulez created?

It was launched in April 2019 to help clean up London’s air.

– What area is currently covered?

Everywhere within the North and South Circular roads.

– How significant is the expansion?

Mayor of London Sadiq Khan is extending the zone to cover all London boroughs from August 29.

– How many vehicles will be affected?

Transport for London (TfL) says nine out of 10 cars seen driving in outer London on an average day meet the Ulez standards, so will not be liable for the charge.

But Driver and Vehicle Licensing Agency figures obtained by the RAC show 691,559 licensed cars in the whole of London are likely to be non-compliant.

This does not take into account other vehicles such as vans and lorries, or vehicles which enter London from neighbouring counties such as Essex, Hertfordshire, Surrey and Kent.

– How bad is air quality in the capital?

An estimated 4,000 Londoners die prematurely each year from conditions related to air pollution, according to Mr Khan.

– How does the Ulez work?

It disincentivises drivers from using the most polluting vehicles by charging them a daily fee for entering the zone.

– How much is the fee?

The charge for vehicles that do not comply with minimum emissions standards is £12.50 for cars, smaller vans and motorbikes.

Lorries, buses, coaches and heavy vans that are non-compliant are charged £100 under the separate low emission zone scheme, which already covers most of London.

– How do I avoid the fee when driving in the zone?

Ensure your vehicle meets the minimum emissions standards.

For petrol cars that means those generally first registered after 2005.

Most diesel cars registered after September 2015 are also exempt from the charge.

– When does the Ulez operate?

All day, every day, except Christmas Day.

– How soon after a journey do I need to pay?

You have until midnight at the end of the third day following the journey.

– Where does the money go?

TfL says all revenue is reinvested into running and improving the capital’s transport network, such as expanding bus routes in outer London.

– What happens if I do not pay?

You may receive a penalty charge notice of £160, reduced to £80 for early payment.