Editing Cutty Sark (section)

====Investigation conclusion====

On 30 September 2008, the [[London Fire Brigade]] announced the conclusion of the investigation into the fire at a press conference at [[New Scotland Yard]]. The painstaking investigation was conducted by the Fire Brigade, along with London's [[Metropolitan Police Service]], Forensic Science Services, and electrical examination experts Dr. Burgoyne's & Partners. They said that the most likely cause was the failure of an industrial vacuum cleaner that may have been left switched on over the weekend before the fire started. The report revealed no evidence that the ship was subjected to arson attack and concluded that the fire started accidentally.<ref name="vacuum"/><ref>{{cite web|url=http://www.london-fire.gov.uk//CuttySarkFireReport-29Sep08.pdf|title=Report on the investigation into the fire on board the clipper ship Cutty Sark, King William Walk, Greenwich, London SE10 on Monday 21st May 2007|author1=London Fire Brigade|author2-link=Metropolitan Police Service|author2=Metropolitan Police Service|date=29 September 2008|access-date=16 April 2010|archive-url=https://web.archive.org/web/20111128063551/http://www.london-fire.gov.uk/CuttySarkFireReport-29Sep08.pdf|archive-date=28 November 2011|url-status=dead|author1-link=London Fire Brigade}}</ref>

Physical evidence and CCTV footage of the fire showed that it probably started towards the stern of the ship on the lower deck. All electrical equipment on board was examined and it was determined that an industrial vacuum cleaner in this area was normally running continuously to suck up dust and particles from work going on to break up concrete within the ship. No one working on the ship had responsibility to ensure all equipment was turned off at the end of each day, and no one recalled switching off the equipment on the Friday in question. The vacuum cleaner has three motors inside and after the fire one was found to be burned out in a manner which suggested it had failed while operating. This was not conclusive evidence, however, because the motor might previously have failed in service without causing a fire, and gone unnoticed because the other two motors had continued to function. Tests on similar cleaners showed they had no thermal cutout devices and while they could run safely indefinitely if filters inside were clear, if the airflow through the cleaner was blocked then it would eventually overheat and could catch fire. This might occur if the cleaner were full of dust and debris. The cleaner had failed previously and two motors had been replaced.

On the basis of witness evidence, the joint investigation team considered it unlikely that the fire was caused by the hot work (welding) that was being carried out as part of the renovation or by carelessly discarded smokers' materials. No one had visited this part of the ship since work stopped on Friday evening, and it was considered unlikely that a fire could have smouldered all weekend before finally breaking out Monday morning. However, it was discovered that although all hot work was supposed to be recorded and someone was supposed to check afterwards to ensure of no fires, there was no record that such checks had ever been made, and on at least one occasion hot work had been conducted with no records made.

The ship was patrolled by two security guards, both of whom were supposed to patrol independently at least once an hour, or once every two hours later in the night, one being primarily responsible for the visitor pavilion and one for the dock. The guards were required to keep a log of their patrols, but after the fire the relevant page was found to be missing from the book. It was later found, already filled in reporting uneventful patrols of the site up to 7 a.m. when the guards would have gone off duty. The alarm was raised when one of the guards called the fire brigade; before this the two reported that they had smelled burning plastic and had been investigating to try to determine its source.

A carpenter had visited the site on Sunday to collect some tools, but after 20 minutes attempting to contact a security guard to let him in, had climbed the fence, collected his tools and climbed out again. The carpenter reported that he had heard machinery operating towards the stern of the ship, but it was not clear whether this might have been the site diesel generator which ran at all times.

The ship was fitted with a temporary fire alarm system but it was unclear whether this had operated. A separate alarm within the pavilion did sound when smoke and heat reached that area, but the guards reported no ringing alarm before the fire was seen. Investigation afterwards discovered a faulty relay in the alarm panel which failed to switch power to the siren circuits when an alarm was triggered. However, the panel also contained a failed fuse in one siren circuit which suggested that the siren had activated but the fire shorted it out, and this might have also caused the relay to fail. The failed relay would have shut off power to the second siren circuit. Statements from workers suggested that weekly tests of the alarm system had not been carried out.