Arlindo Visentin, 58, died helping three other workers build a basement at the private property when he was crushed by a collapsing wall of gravel and clay weighing between three and five tonnes.

Contractor Nadeem Aftab, Visentin’s employer was today fined £100,000 following the tragic incident in Wilton Row, Westminster.

The Health and Safety Executive prosecuted Aftab of Rosebury Road, Fulham, who pleaded guilty to safety breaches. He was also ordered to pay costs of £61,590.

City of London Magistrates’ Court heard that on 13 June 2007 Visentin was working in the basement area when the collapse took place, completely burying him with clay and gravel, causing fatal crush injures.

The HSE investigation found the temporary works required to support the earth during the underpinning operation were not adequately planned.

The earth that remained following the underpinning of the walls was not properly supported, and at the time of the incident no measures were in place to prevent falls into the excavation.

Aftab failed to make sure the workers on site were trained, qualified and competent to carry out underpinning.

Following the hearing, HSE Inspector, Lisa Chappell said: “Mr Visentin spoke very little English and did not share a common language with any of the other workers or with Mr Aftab.

“This incident highlights the need to have effective worker consultation and communication with all employees to ensure they understand the control measures that should be in place to prevent harm.

“Basement conversions involving underpinning are significant engineering projects and should be planned and managed by competent people.

“As a part of this, a competent temporary works engineer should design an appropriate sequence of works, and the work should be actively managed by a person who had the necessary knowledge, training and experience to ensure it is carried out safely.”