The most likely source of the fire that caused extensive damage to the historic Cutty Sark tea clipper was a faulty industrial vacuum cleaner, say police.

A joint investigation by the Metropolitan Police, London Fire Brigade and Forensic Science Services studied physical evidence and CCTV footage to discover the failure of a motor inside the industrial vacuum cleaner being used to remove waste from the ship as part of its £25m renovation was the most likely cause.

Fire crews were called to the ship in the early hours of May 21, 2007, with eight engines and more than 40 firefighters tackling the blaze.

The Cutty Sark Trust has said just 5% of the original fabric of the ship was damaged in the blaze, with much of the original timber already removed for cleaning and restoration.

In June, Israeli shipping magnate Sammy Ofer donated £3.3m to complete the funding of the ship’s restoration.