The 370-tonne turbine is on the final leg of its journey from Mannheim in Germany to the gas-fired power station where it will be housed in north London.

Three 40-tonne tractor trucks have dragged the turbine at 4mph from Tilbury docks to junction 31 of the M25 and from there to junction 25.

The massive load is now crawling along the A10 and is scheduled to reach its final destination in Enfield at about noon on Sunday.

There have been long traffic delays behind the convoy and they are expected to continue until the turbine is safely off the road.

'Biggest load ever'

The rig set out on Saturday night. It weighs 650 tonnes loaded and is 100m long, while the turbine's specially-constructed 60m trailer alone is 160 tonnes and has 26 axles and 102 wheels.

The load has caused traffic headaches

Highways Agency Project Manager Ing Fischer said: "We believe this is the biggest load ever to travel on a motorway road in this country.

"It is a big operation and has taken a year of precision planning for the agency, the police and the haulier.

"In the process we have had to assess structurally 50 bridges to make sure they can carry the load."

Traffic signals and bollards on the A10 have had to be temporarily dismantled to create enough space for the turbine.