The secrets of Dunsby Fen

Did an embittered heiress seal up the cellar of this farmhouse? The 'House Detectives' solve the mystery.

A Desolate Lincolnshire fen is the setting for this week's edition of The House Detectives. Caroline and Paul Mentzel stumbled across Dunsby Fen Farmhouse while they were on holiday with their four children in 1995. The family had to live in a caravan while they restored the house.

Dunsby Fen Farmhouse, with its grand appearance, is one of those houses that appeals to the dreamer, and an air of mystery enhances rather than diminishes its attractions.

Local legend has it that the house's cellar was blocked off by an embittered heiress. Another mystery is why the main entrance of the house seems to be tucked away on the side of the house without any drive or path leading up to it. However, photographs show that in the house's heyday there was a smart driveway leading up to the entrance, which has now been covered by a lawn.

The interiors are of a remarkable quality, with an elaborate frieze, highly decorative plates on the main door, and a grand staircase. Who had the time and money to lavish this expense?

Judging the house by the landscape in which it is set gives some useful clues. Studying its position on the Ordnance Survey map the house seems to have been part of the grand drive to cultivate the once waterlogged land during the mid 18th century, when it was finally enclosed and drained.

The Forty Foot drain is the main drainage channel for the Black Sluice area on which the farmhouse is built and is large enough to carry boats. And so house detective David Austin decides to take a boat trip as part of his fact finding mission.

Census returns and local wills dug up by archivist Penny Olsen show the Casswell family lived at Dunsby Fen for over 100 years. Further research in the Lincolnshire County Records office reveals that the site was originally owned by Charterhouse, a charitable trust, which led the detectives to London to examine the relevant documents.

It would appear, from the layout and design of the house that it was built in the late 19th century on the site of an earlier property. Proof comes with documents that show a house first being built in 1771 by a tenant, William Carter. The bricks used would have been hand made on site out of Fen silt. In 1842, a new tenant arrives, Thomas Casswell, who rebuilt the farm in 1870. The Casswells also gave their name to a local bridge.

And the mystery of the cellar? The layout of one set of stairs suggests a strong likelihood of a cellar underneath, but plans of the old house suggest it was, in fact, the site of a lavatory.

Undeterred, Mac Dowdy resorts to a tried and tested technique, with Nina, the Mentzel's daughter, and brings out the dowsing rods, last seen in action at Mulberry Cottage.

Once again, the rods seem to show there is something there. But it is not until they get out a pneumatic drill, and make some small holes, are they able to find conclusive proof. Underneath the stairs, there is a space, filled in, but none the less the site of the old cellar. Mystery solved.