The parents of a lawyer crushed to death by window frames weighing half a ton are calling on construction companies to stop ignoring public safety, after a supervisor was found guilty of her manslaughter.

Amanda Telfer, 43, died when a stack of large unglazed frames, weighing 655kg, toppled on to her as she walked past a building site in Hanover Square in Mayfair on August 20, 2012.

Members of the public tried to save her but the injuries sustained by Ms Telfer were too great and she was pronounced dead at the scene just before 12.  

Four people and three companies denied any responsibility, and 13 charges relating to her death.

However, during a six-week trial, a jury found Kelvin Adsett, supervisor at IS Europe Limited, guilty of manslaughter and breaching health and safety.

IS Europe Limited, of Slough, was found guilty of two health and safety breaches at the Old Bailey.

Damian Lakin-Hall, an employee of Westgreen Construction Limited, was convicted of failing to take reasonable care of safety whilst at work.

Ms Telfer's parents Barry and Ann Telfer described Amanda as a "bright lovely professional woman" who lived life to the full. 

They said: "Her future was taken from her when she was crushed to death by half ton window frames which took two seconds to fall on her.

"The frames had been left standing, almost vertically, at the side of a public pavement, unsecured to anything, unattended and with no safety barriers around them.

"If construction companies and the people who work for them are not held to account for such high levels of negligence and incompetence, then none of us is safe walking the streets next to construction sites.

"The Health and Safety training being given is totally inadequate, if risk of death to passers-by is ignored.

"It is nearly five years since Amanda died.

"We would like to thank the police, Health and Safety officers and prosecution who worked on behalf of Amanda for their persistence and patience.

"We and all Amanda's family and friends will always miss her. Nothing will change that."

Prosecutor Duncan Atkinson QC said it was "obvious to anyone" that they carried a "clear and serious risk of death" to anyone walking past.

Before the accident, members of the public had expressed concern about the danger posed by the frames as they could be seen blowing in the wind.

There had been a "near-miss" at the site days before the fatal incident, the court heard.

Mr Atkinson said: "There were a series of obvious and, in many cases, straightforward steps that could have been taken to avoid that risk, ranging from cancellation, delay, refusal of delivery on the one hand, to the storage, the use of straps and barriers.

"None were taken by any of the defendants and Amanda Telfer died as a result."

Ms Telfer was working as a freelance intellectual property and media lawyer for publishing houses including Random House at the time of her death.

Lakin-Hall, 48, of Portsmouth Road, Cobham, Surrey, and 65-year-old Adsett - also known as Kelvin Schultz - from New Road, Slough, Berkshire, denied manslaughter and health and safety breaches along with Claire Gordon, 36, of Ashby Crescent, Leeds, who was cleared.

Steven Rogers, 62, of Sheering Mill Lane in Sawbridgeworth, Hertfordshire, was found not guilty of a single charge of failure to take reasonable care for safety while at work as an employee of Westgreen Construction Limited.

Westgreen Construction, of Richmond in Surrey, and Drawn Metal Ltd, of Leeds, were also cleared of health and safety charges.

Judge Peter Rook QC adjourned sentencing until May 5.