Leon Max, Russian-born owner of women's fashion company, Max Studio, bought Easton Neston, near Towcester, in 2005 for £15m from former Conservative chief whip in the House of Lords, Lord Hesketh.

However, one of the conditions placed on the planning application to convert the Wren Wing to offices in 1978 was that only former owners Fermor Hesketh Estates could use the building for business purposes.

The Development Control Committee at South Northamptonshire Council approved an application from Max Studios to lift the condition on Thursday.

Alan Munn, case officer, said: "A few years ago the estate was sold and the new occupants wanted to use the building as a base for their business activities but because of the restrictive occupancy condition, they could not do this until they had applied for planning permission to get the condition removed.

That was the application, which went to committee last week.

"It was approved and means that the applicants can now use the building as a base for their business, provided that the activities undertaken falls within the B1 use class."

The original condition was found to be unnecessary by the committee, allowing Max Studios to manage its European operations from the Grade I listed building, which has been restored since it was damaged by a fire six years ago.