PLANS will be formally submitted next week to build 400 houses on a corner of a country estate to help fund the restoration of its historic castle.

Trustees of the Lambton Estates, near Chester-le-Street, have revealed details of a £28.5m makeover of the 1500-acre estate ahead of an application for outline planning permission, due to be submitted to Durham County Council on September 1.

A parcel of land on the southern edge of the estate would be developed for mainly executive housing, although 15 per cent would be designated affordable homes, along with 86,000 sq ft of offices and 7,500 sq ft of retail and community uses.

The development would allow money to be ploughed into restoring the estate’s historic assets including the Grade II-listed Lambton Castle, which featured in the BBC period drama The Paradise.

Trustees say the public have had little chance to access the estate since the closure of the famous Lambton Lion Park in 1982.

They say the proposals for “Lambton Park” would create around 12km of walking and cycling routes and open up acres of parkland to the public with views of both Lambton Castle and the Grade I-listed Biddick Hall.

The development will fund investment into more than 50 projects to protect the estate’s heritage assets, including £1.8m to repair the castle’s retaining wall, £2.1m on the castle stables and £600,000 to stablise the Grade II-listed Lamb Bridge, an 80-ft single span bridge built in 1819 by Ignatius Bonomi.

David Gray, of estate managers GSC Grays, said: “The Estate is one of the region’s hidden gems containing nationally and regionally important heritage assets.

“Despite past efforts and recent investments many of the properties and historic grounds continue to decline.

“Lambton Estate is now at a critical point in its history; it requires a long-term, viable framework to secure its future and preserve this nationally important heritage asset.”

He added: “With the ongoing deterioration of a number of its notable heritage assets the Estate is considered to be at a tipping point in terms of its long-term viability”.

Lambton Estates has appointed planning consultants Nathaniel Lichfield and Partners to deliver the project.

Director Michael Hepburn said the proposals are being submitted now as “further delays may well impact on the viability of an application in the future”.

Lambton Park has been designed with the help of well-known London-based architect Ben Pentreath, who advised Prince William and the Duchess of Cambridge on the upgrade of their Kensington Palace home.