PAXTON Pits nature reserve is set to treble in size to become one of the largest in Cambridgeshire. The phased release of exhausted quarry land as far downstream as Diddington over the next 10 years will see the reserve expand in size from less than 200 acres now to more than 700 under an agreement signed between the district council and landowners. The reserve already attracts more than 120,000 visitors a year. One of the landowners involved is Edmund Thornhill whose family owns most of Diddington and who is paying for a new £200,000-plus access road that will open on Sunday. He is putting around 200 acres into the Paxton lakes expansion on an 80-year lease at a peppercorn rent.