In medieval times, military training took place near the castle, on a large open area of land called The Flatts. The woods which bounded this area to the north and west became known as Flatts Woods.

The Woods formed part of Marwood Chase, the hunting park of the Baliol family, who were the lords of Barnard Castle. In the 13th Century, Hugh Baliol granted the townspeople the right to graze their pigs in the woods.

Since about 1630, the woods have been owned by the Vane family of Raby Castle, the seat of the present Lord Barnard. About 200 years ago, Flatts Woods began to be laid out with paths for the pleasure of residents and visitors.

First, Dr. George Edwards (1750-1823), at his own expense, made paths giving access to walks along the Tees Banks and, during the 19th Century, the paths were developed farther into Flatts Woods, with footbridges gradually replacing fords and stepping stones across Percy Beck. ('Beck' is an old Norse word for a stream).

Percy Beck forms a boundary between the parishes of Marwood and Barnard Castle and cast iron boundary markers can be seen at each end of the old