The Blitz is considered to have ended in mid-May 1941, though periodic raids continued, such that against Southampton in July.Collier, Chapter XIX. By October 1941 the availability of SLC radar was sufficient to allow AA Command's S/L sites to be 'declustered' into single-light sites spaced at 10,400-yard intervals in 'Indicator Belts' in the approaches to the GDAs, and 'Killer Belts' at 6000-yard spacing to cooperate with the RAF's night-fighters.Routledge, pp. 399–401.
