Public liability insurance holders have been warned about the "duty of care" which construction site managers have towards workers after the prosecution of a contractor.
Chris Byrne, of Christchurch Avenue, Brent, was found guilty of breaching Regulation 5(2) of the Construction (Health, Safety and Welfare) Regulations 1996 and was fined £750, along with costs of £750.
Westminster Magistrates' Court heard how, in 2006, a labourer started work extending a house in Wembley for his contractor, Mr Byrne.
He was instructed to fill earth around concrete blocks next to the extension and, when Mr Byrne returned to the property, the worker was found head first in a pit with water up to his waist.
Monica Babb, Health and Safety Executive (HSE) inspector, said that those running construction sites, whether they are domestic or commercial jobs, have a duty of care to supervise vulnerable workers on their sites.
Earlier this month, the HSE issued a warning to public liability insurance holders about a duty of care towards employees after the prosecution of Aram Resources of Penryn.
It followed the death of a worker who was caught in the fixed guard of a primary crusher machine.