The company developing Enfield Town has won the £57million project to revamp the dilapidated junction of the M25 on the outskirts of the borough.

Costain Limited, which is constructing the PalaceXchange shopping complex, will embark on the multi-million pound scheme to refurbish Junction 25 of the motorway and the run-down Holmesdale Tunnel, after winning the contract last week.

The Maidenhead-based company, which has been established for 140 years, will begin work on the London orbital motorway later this year. It is expected to be completed by spring 2007.

Work to increase the number of lanes through the tunnel, from two to three in each direction, will also be completed by 2007.

Government transport minister Dr Stephen Ladyman welcomed the news.

He said: "This project will provide improvements to safety and reduce congestion and journey times by cutting accidents and delays on the eastbound M25 at junction 25 and improve the flow of traffic through the tunnel.

"Refurbishment of the tunnel will be to UK standards, using the best international tunnel practice. We are committed to improving the road network and providing safer and smoother journeys to motorists."

The Highways Agency, which drew up the plans and awarded the contract to Costain, has already held two public exhibitions in Enfield to inform motorists about the planned changes to road layouts and the likely delays.

The project will replace ageing mechanical and electrical equipment in the Holmesdale Tunnel, and improve the eastbound carriageway.