During the Second World War, barrage balloons were used to protect urban centres and other important locations, such as ports and factories.
In the Battle of Britain and the Blitz, they offered a vital means of defence against the Luftwaffe as their trailing metal cables would severely damage or destroy any aircraft which touched them.
Attackers attempting to shoot down a balloon could be caught in an explosion of the hydrogen used to get them airborne. German bombers also had to fly above the balloons, reducing their bombing accuracy.
Balloon Command was formed on 1 November 1938 with its headquarters at RAF Stanmore Park. Its squadrons were unusual in that they were made up of volunteers of the Auxiliary Air Force. Women were also recruited, employed as fabric workers and as winch operators who brought the balloons back to the ground.
Balloons could be flown from ships or barges at sea, from fixed sites on land, or from mobile sites. They were usually tethered by cables to concrete blocks, which were set in a circle in the ground.