Porsche Spyder 918
The Porsche 918 Spyder has a top speed of around 340kmph (210mph) Porsche

A Saudi millionaire blocked traffic in one of the busiest roads in London by having his £540,000 supercar washed in public.

Motorists and buses were forced to slow down and change lanes in Brompton Road, Knightsbridge, while the Porsche 918 Spyder was cleaned and detailed by two men for around an hour, the Daily Mail said.

The hybrid car was washed in an on-street parking space, but passing vehicles were forced to move into other lanes in order to avoid its open doors.

It reportedly belongs to a nephew of Saudi Arabian rally driver Yazeed Al-Rajhi and has been brought over from Saudi Arabia for the supercar season.

"The Porsche 918 Spyder arrived filthy and when a valeting van arrived we joked it was here to clean the Porsche," said Paul Wallace from the 'Supercars of London' YouTube channel.

"But it was. For around the hour, two guys washed the car on arguably the busiest road through central London, Brompton Road.

"It was comical and certainly stopped the general public as they walked by.

"There are a couple of well-known valeters and detailers in London that provide car owners the privacy and security, but it seemed this owner didn't care and wanted it done quickly."

The Porsche 918 Spyder is a limited edition hybrid sports car with a steep starting price of £540,000 (€770,000, $847,000). It has a top speed of about 340kmph (210mph).