A 48-year-old man has been arrested by French police investigating the murder of the Al-Hilli family from Claygate, prosecutors have said.

Saad Al-Hilli, 50, of Oaken Lane, his dentist wife Iqbal, 47 and her mother, Suhalia Al-Allaf, 74, were shot dead in their BMW while on a camping holiday in the French Alps on September 5, 2012.

A French cyclist Sylvain Mollier, was also shot dead on the remote forest road in Chevaline, near Lake Annency.

The two Al-Hilli children, both former pupils of Claygate School, survived the attack.

Zainab, then seven, was shot and pistol whipped by the gunman but survived the attack and Zeena, then four, escaped unharmed after she hid beneath her mother’s skirt.

Atention has turned to Mr Mollier as the possible intended target since Saad's brother, Zaid Al-Hilli, who lives in Chessington, was released from police bail.

The man, said to be from the Haute-Savoie region, was placed in formal police custody. In November police released an e-fit of a motorcyclist they wished to speak to in connection with the murders, who was thought to be in the region at the time.

Annecy prosecutor Eric Maillaud said: "This arrest, which may not be the only one, was the result of witness statements that came in after the image was released."

About 100 police officers in Britain and France have been working on solving the killings.