A watching brief on drainage works and depth-limited soil-stripping with a large compost-processing site at Birch airfield resulted in the discovery of linear features and pits dating from the late Iron Age/early Roman period onwards. The observations were too fragmentary to yield an integrated picture of the earler activity, but include ditches and gullies belonging to the field systems, possibly with associated structures. The nature and distrubution of finds suggests that a focus of Roman occupation lies within or in the immediate vicinity of the north-western corner of the airfield.