A whole series of management failures led up to the Battersea crane disaster in 2006 a jury decided on Monday, but the coroner refused to allow them to return a verdict of unlawful killing.

The 37-year-old crane driver Jonathan Cloke and 23-year-old bystander Michael Alexa were killed when the 165ft tower crane collapsed in Thessaly Road after it was overloaded by Falcon Cranes employees using the wrong manual.

The inquest also heard that several vital slew ring bolts had failed two months before the catastrophic collapse, but the company had failed to adequately investigate the cause.

After a week-long hearing, the jury sitting at Westminster Coroner’s Court detailed a whole series of mistakes by Falcon Cranes that fatally jeopardised the safety of the crane, and highlighted a “vacuum” of structured management in its service department.

But despite all the evidence of failures by the company and to the amazement of the victims’ families and their lawyers, coroner Dr Shirley Radcliffe denied the jury the option of delivering a verdict of unlawful killing against the company, which would have opened the way for a criminal prosecution.

She ruled that even though the company was using the wrong manual, the procedure it used to replace the failed bolts was the right one and there was no gross breach of the duty of care by Falcon Cranes.

Instead, the jury rejected an option of delivering a verdict of accidental death and chose to deliver a narrative verdict, which was read out in court.

It said: “Both men died as a result of a crane collapse due to failure of the inner slew ring bolts due to overloading of the counterweight.

“The overloading was due to an incorrect manual being used in the erection of the crane.

“On July 25, 2006, four inner slew ring bolts failed and all of the slew ring bolts were replaced. No investigation was undertaken as to the root cause of the bolt failure.

“On July 26, 2006, the crane was returned to service.

“At that time there was no adequate formalised process and procedure to allow for faults to be managed, escalated or investigated. In addition there was a vacuum of structured management in the service department.”

Speaking after the verdict Liliana Alexa, Mr Alexa’s mother, said: “The bolts needed to be replaced at least every eight years but this crane had no history when Falcon bought it in 2002, so who knows how old the bolts actually were?

“We have been let down for six years and feel exactly the same now. We have to speak to our solicitors to find out what to do next.”

Louise Christian, of law firm Christian Khan, the solicitor representing the Alexa family, said: “The decision of the coroner not to allow the jury to consider a verdict of unlawful killing was baffling in the extreme.

“The coroner found the managing director of Falcon Crane Hire Ltd, Douglas Genge, owed a duty of care to the family and had breached that duty of care.

“However, she stated that the deaths of Mr Alexa, a member of the public, and Mr Cloke, the crane driver, may not have been caused by the breach.

“Mr Genge accepted in evidence that the crane should not have been put back into service until the cause of the exceptional near collapse of the crane was ascertained.”

Ms Christian said the Alexa family would be looking at the possibility of a judicial review of the corner’s decision.

The Battersea crane disaster led to the setting up of the Strategic Plant Forum for Safety to regulate and monitor crane safety.

Before the incident, there was no recognised examination to become a tower crane supervisor and no guidelines when buying a crane.

Now, cranes have to be fully registered and have a detailed history that can be checked by those hiring the machinery.