The 19m (62ft) Cujo went down 21 miles (35km) off Beaulieu-sur-Mer after sending out a mayday call last Saturday.

The seven people on board the luxury vessel, which was taking on water, were rescued by teams from Antibes before it sank to the bottom of the Mediterranean at a depth of 2500m (8200ft).

They were safely returned to shore.

The area was monitored for pollution as the boat sank with 7,000 litres of diesel in its tanks.

Cujo made front page news around the world back in the summer of 1997 when Al-Fayed entertained Diana onboard, a year after her divorce from Prince Charles, which was finalised in August 1996.

That summer, Diana was also photographed on Sokar, the yacht then owned by al Fayed's billionaire father Mohamed.

It had previously been named Jonikal.

Cujo was built in Italy in 1972 for businessman John von Neumann who told the Italian Baglietto shipyard that he wanted the world's fastest motor yacht.

She was fitted with two 18-cylinder engines giving her a top speed of 42 knots.

Van Neumann then sold the boat to the son of Saudi businessman and arms dealer Adnan Khashoggi and he sold her on to his cousin, al Fayed.

Cujo was frequently moored off St Tropez, a famous celebrity hangout on the French Riviera, with guests including Clint Eastwood, Tony Curtis and Bruce Willis.

Following the death of Diana and Al-Fayed in central Paris on 31 August 1997, Cujo fell into disrepair.

She was decommissioned in 1999, and spent years in storage, before being restored by new owners.