We nearly said the App would tell you where there is a free space, but "free" is not the word to use in conjunction with Westminster, where parking currently costs up to £4.40 per hour.

The idea is that sensors in the road will alert drivers to unoccupied parking bays. That means less aimless driving around and potentially less congestion, as up to 30% of urban traffic is made up of people trying to park, which seems ironic – some traffic jams are apparently caused by people who are trying to stop driving.

The trial will cover five streets - Savile Row, Jermyn Street, Sackville Street, St John's Wood High Street and Burlington Gardens, and will run from August 15 to October 15.

However it is not all good news for the motorist. The sensor will know exactly how long the car has been parked, so there is no point chancing a five minute overstay. Also Westminster Council will be able to track the demand for spaces in specific areas, so drivers can expect even higher charges for particularly popular streets.

Overall though, it has to be a good thing to maximise the use of available spaces. It should also hinder those parking wardens who hand out fraudulent tickets – if the sensor shows the car was correctly parked, it will be harder to fake an offence.