The Canary Wharf crane collapse in May 2000 killed three construction workers and bereaved three families. Last week's inquest heard their harrowing story – but offered no answers. Marguerite Lazell reports from St Pancras coroner's court
Allison Clark, Janine Wood and Melanie Whittard sat cramped on the hard bench seats of St Pancras coroner's court and wept as they heard witnesses describe how their partners had died in a crane accident at Canary Wharf in May 2000. Last week, the jury returned an open verdict after the four-day hearing, unable to satisfy themselves that, in the balance of probabilities, the deaths had been accidental. The open verdict means that the three families could mount a civil case against the men's employers in the future.

The incident happened on the afternoon of Sunday, 21 May, on the site of the HSBC tower. John Cashing, a crane operator who had been leaving the site at the end of his shift, told the court how he had heard a huge bang from TC-3, the tower crane that Michael Whittard, Peter Clark, Martin Burgess and their team were working on. "The back Ballast started twisting, the jib went backwards right over the top," he said. "I saw a brace from the climbing frame on the road as I went running back from the car park." fCashing raced to the scene to find the three men crushed under the wreckage. Peter Clark, who had been driving TC-3, was trapped in his cab.

The court heard that the three men would have died instantly from the impact of the 450 ft fall. The coroner warned the jury of the distressing nature of the the photos taken by the Metropolitan Police before admitting them as evidence. He told them that routine toxicology investigations had found no traces of alcohol or drugs in any of the three men's bodies, and that the cause of death was from multiple injury in each instance. The central question was how the crane came to collapse.

At the time of the incident, Michael Whittard and his team were all employees of Hewden Tower Cranes. The men had travelled down from Castleford in Yorkshire to extend the height of TC-3 so that steelwork contractor Cleveland Bridge could continue work on the HSBC building. Although none of the three bereaved women knew much about the technical aspects of the men's work, they were all too aware of the hours they worked. Gareth Hetherington, a colleague who had been slightly lower down on the crane during the climbing operation, told the court that the team worked 80-100 hours a week, starting as early as 6.30am on site.

  Eamonn Glover, who had been with Hetherington on TC-3, said that they were just minutes away from finishing their weekend's work when the crane collapsed at about 4pm.

"It was the last piece of the day, the new section was hung in place," he said. "It would've been 15 minutes to secure all the pins. We were a bit behind schedule, but we should have been travelling back north to our families by 4.30pm." Both Hetherington and Glover told the court that they had feared for their lives as the crane started to shake. "The climbing frame started to twist, and everything started creaking," recalled Glover. His mind went momentarily blank as he clung desperately to the hand rail of the mast of the crane as the top section and climbing apparatus were ripped away.

It was policy to put a wind gauge on every crane. Whether or not one was fitted was another matter

Patrick Yates, Hewden Tower Cranes

The collapse was triggered when a massive torsional force pulled the north-east guide wheels out of alignment on the climbing frame, sending the entire structure out of balance. The rotational movement caused the brace of the climbing frame to break away, and as the luffing jib fell backwards the top part of the crane became detached from the mast and fell across the construction site. The wreckage was found across North Colonnade road, with the brace that had broken away on another part of the site. The crane hook struck a pedestrian precinct 120 metres from the base of the crane.

The Heath and Safety Executive has carried out extensive investigations into the tragedy, but has been unable to pinpoint the exact cause of the crane's collapse. The court heard from HSE investigator Mike Williams and expert witness Graham Norton, a specialist engineer.

Williams' task was made difficult by the almost total lack of documentation relating to the climbing frame kept by Hewden Tower Cranes. The operations manager at the time, Patrick Yates, told the court that there were no records kept of where and when the frame was used, or if and when any maintenance was carried out. He did not know when the company had acquired the frame, and could only guess at its expected lifespan. He appeared confused when questioned about the exact whereabouts of the frame in the months leading up to the incident: he had thought it had remained at the site throughout, whereas Gareth Hetherington told the court that he knew it had been dismantled to be taken elsewhere for another job at least twice.

TC-3 was not fitted with an anemometer, despite strict guidelines determining the wind speeds at which using the crane and climbing frame became unsafe. "It was policy to put one on every crane," Yates said. "Whether or not one got fitted was another matter. It should have had one when it was first erected." On the Saturday before the accident, the crew had been "winded off" from the job after receiving information from one of the other cranes, TC-1, which did have a wind gauge.

Specialist engineer Graham Norton conceded that wind may have been a contributing factor in the collapse, but said that he was unable to find one single force that had caused the overload failure to the guide wheel. Metallurgy investigations into the climbing frame found no evidence of fatigue damage to the struts or the wheels, despite Hetherington's recollection of part of the frame bowing slightly during earlier climbs. Norton confirmed that when he and his team examined the slewing module its condition suggested the brake was on. If this was the case, an unintentional slewing motion during the climbing operation which could have set the crane out of balance was unlikely.

A hard lesson: Safety proposals

In the light of evidence heard at the inquest, the HSE will now continue its investigation, and so cannot comment on the incident. A discussion paper has been issued by the HSE on the safe use of external climbing frames.

The British Standards Institute will take the information in this discussion paper into account at the next planned revision of the British Standard on tower cranes. The HSE’s design recommendations will be taken to CEN (the European Committee for Standardisation), and to the committee for crane standards within the ISO, the International Organisation for Standardisation.

The discussion paper suggests that suppliers should provide certified training for employees using climbing frames, as there is currently no formal training. It also proposes that climbing frames should be given a thorough examination before first use, and inspected before each subsequent use.

The paper suggests introducing comprehensive procedural guides, covering transportation, assembly and dismantling of frames, obtaining site-specific weather forecasts and carrying out risk assessments as part of site preparation.