Kristian Childs, trading as KD Childs Stonework of Luton, had been sub-contracted to install stone fireplaces in new homes, including one in Coulthard Close, Towcester, which was subsequently bought by David and Gail Green.

They moved into the property with their son Matthew and older daughter Rachel in June 2003.

On 15 October 2005 the 47kg mantel from the fireplace came away from the wall without warning and fell on Matthew. He was airlifted to hospital but died of his injuries shortly afterwards.

An HSE investigation found that Childs had secured the mantel with small patches of mortar rather than mechanical fixings.

Northampton Crown Court heard that Childs was aware of the need to ensure fireplaces were properly secured after two others he had fitted at other properties were found to be insecure by the home owners.

Childs of Sundon Park, Luton, pleaded guilty to safety breaches and was fined £7,500 with £2,500 costs.

After the hearing Alan Craddock, Head of Operations for the HSE’s Midlands construction division said: “This was a tragic incident that devastated a young family, made so much worse by the fact it could have been so easily prevented.

“Every stone used in a fireplace must have a mechanical fixing, such as a steel bracket and screws, to hold them together and against the wall.

“A few small patches of mortar are not acceptable because it cannot guarantee a secure bond.

“Mr Childs was well aware of the risks of falling fireplaces yet failed to take the correct steps to ensure the fireplace he fitted at Coulthard Close was safe, with appalling consequences.”

Matthew’s mother, Gail Green, said: “Losing Matthew was devastating. We miss him every day and will never truly recover from the events of that day.

“We urge anyone involved with the installation of fireplaces to learn from what happened to our precious son and take steps to ensure that they take the time and trouble to fit them properly.

“If they don’t then lives will continue to be put at risk and Matthew’s death will have been in vain.”