Swann Auction Galleries said: "Rarely, if ever, has a piece of an 18th Century map's publication story been preserved or offered for sale." A specialist assessed the map to be about 75% complete.

The plan shows the town in "extraordinary" detail for a 18th Century manuscript, according island archivist Dr Darryl Ogier. Dr Ogier said the map was "far more detailed than anything else we've ...