Four gilt-bronze sconces that lit up home of Louis XV’s mistress are set to go on sale at Sotheby’s in December

For almost 140 years, four massive gilt-bronze wall lights have hung in the 18th-century drawing room at Swinton Castle in Yorkshire, now an opulent luxury hotel.

Guests will almost certainly have noticed the one metre-high rococo appliques with their entwined branches decorated with leaves, berries and cherubim, and passed them off as impressive reproductions of more valuable original works.