Operation Diver

Anti-aircraft guns proved the most effective form of defence in the later stages of the campaign, with the aid of radar-based technology and the proximity fuse.

Anti-aircraft guns were redeployed in several moves: first in mid-June 1944 from positions on the North Downs to the south coast of England; then a cordon closing the Thames Estuary to attacks from the east.

The average altitude of the V-1, between 2,000–3,000 ft (610–910 m) was in a narrow band above the optimum engagement height range for light 40 mm Bofors guns.

By mid-August 1944, the threat was all but overcome by the expedited arrival of two enormously effective electronic aids for anti-aircraft guns, the first developed by the Radiation Laboratory at the Massachusetts Institute of Technology (MIT Rad Lab) radar-based automatic gun-laying (using, among others, the SCR-584 radar) and the proximity fuze.

Machine-gun bullets had little effect on the sheet steel structure and 20 mm cannon shells were explosive projectiles; detonating the warhead could destroy the fighter as well.

In daylight, V-1 chases were often chaotic failures, until a special defence zone between London and the coast was declared in which only the fastest fighters were permitted.

The experimental jet-powered Gloster Meteor, which was rushed half-ready into service in July 1944 to fight the V-1s, had ample speed but suffered from unreliable armament and accounted for only 13 bombs destroyed.

MI5 (by way of the Double Cross System) had these agents provide Germany with damage reports for the June 1944 V-1 attacks which implied that on average the bombs were travelling too far, while not contradicting the evidence presumed to be available to German planners from photographic reconnaissance of London.

In September 1944, Duncan Sandys announced that the "Battle of London" against the V-1 was effectively over, as the launch sites in France had been overrun by Allied ground forces.

The Germans had prepared sites in the Netherlands, from which they launched V-1 attacks against Antwerp and Brussels starting in October 1944, against which Operation Vapour was mounted.

V-2 bombardments began in September 1944, and the last enemy action of any kind on British soil in the war occurred on 29 March 1945, when a V-1 struck an empty field near Datchworth in Hertfordshire.