£40m robbery is Britain's second biggest

XL is the lead insurer for Graff, the London jewellers raided by two gunmen in a £40m robbery, Insurance Times understands.

Market sources said earlier that Willis was the broker in what Metropolitan Police called the second-biggest robbery in Britain, only exceeded by the £53m raid on a Securitas depot in Kent in 2006.

The robbery at New Bond Street, in which 43 high net worth items were taken, happened on 6 August, but details were only revealed by police last week.

Female staff members were dragged outside by two smartly dressed men, who fired a shot, although no one was injured. They escaped in a blue BMW.

It is believed the robbers used liquid latex, scalp masks and wigs to transform themselves at a professional make-up studio hours before the robbery. One of the suspects is already thought to have been identified though DNA tracing.

Detective Chief Inspector Pam Mace of the Flying Squad said: “This was a well-planned robbery with a number of vehicles used to help the robbers escape.

“These men are extremely dangerous, and fired at least two shots in busy London streets as they made their getaway.” Mace added: “Someone knows who these men are. They would undoubtedly have spoken about it beforehand or boasted about it afterwards.”

Willis reportedly won the contract for Graff in 2007 and was the broker last year. The situation is not thought to have changed.

Willis and XL declined to comment.