World War II Pickett-Hamilton Fort Su 4681 3512 (No.1), Worthy Down Airfield

This is a four-man counterbalance Pickett-Hamilton fort dating from around 1940, located at the former RAF Worthy Down Airfield. The fort is constructed of concrete and steel.

The fort consists of a circular concrete form visible at ground level, approximately 3.7 metres in diameter. It comprises a central circular concrete roof belonging to the lifting fort and an outer concrete ring. The outer ring contains two metal access hatches positioned to the north and south, each fitted with double doors. The hatches provide access to metal rungs in the external fort wall, which allow descent into the interior. Both the interior face of the external wall and the external form of the lifting fort retain visible gun loops and the fort's metal supports. Some debris and water ingress are present at the bottom of the fort.

Pickett-Hamilton forts were developed by Francis Pickett and Donald Hamilton from summer 1940 onwards as part of comprehensive airfield defence schemes. Many were constructed by the New Kent Company of Ashford. They were typically built in groups of three and located on flying fields. These fortifications were uniquely designed to remain flush with the ground surface, allowing aircraft movement across the airfield, but could be raised to enable manning and provide cross-fire during enemy attack. They consisted of two reinforced concrete cylinders, one inside the other. The most common two-man design featured a single access hatch and was raised by hand-operated hydraulic jack. The rarer four-man counterbalance type, of which this is an example, featured two access hatches in the outer ring and used a counterbalance mechanism for raising. Approximately 240 Pickett-Hamilton forts were constructed in England, of which only about a dozen were of the counterbalance form.

RAF Worthy Down was established on the site of the former Winchester Racecourse, requisitioned by the War Office for the Wireless and Observers School of the Royal Flying Corps, opening in August 1918. The RAF occupied it continuously until May 1939, hosting several Bomber Squadrons during the 1920s and 1930s. It then passed to the Navy, becoming HMS Kestrel, occupied by Fleet Fighter Squadrons 800 and 803. After the war it became a Rehabilitation and Vocational Training Centre, closing in 1950. It reopened two years later as HMS Aerial II, housing the Air Electrical School until late 1960 when the school departed and the airfield closed. The Royal Army Pay Corps subsequently occupied the camp to the east. The former airfield is now under arable cultivation.