The 1940 decoy airfield at Boulmer was one of dozens scattered across Britain, built to lure Luftwaffe attacks away from operational bases such as nearby RAF Acklington. The trick relied on a peculiar mix of theatre and engineering: grass laid out to look like runways, lighting rigged to mimic flarepaths at night, dummy aircraft constructed from wood and painted canvas. From altitude, in moonlight, the illusion held. As the Battle of Britain receded and German bombing shifted away from northern England, the Boulmer decoy was wound down. In March 1943 the field was reopened with real aircraft this time - a satellite airfield housing the advanced flights of No. 57 Operational Training Unit, where pilots completed Spitfire training before going to operational squadrons. Part of the wartime runway is now an access road through a caravan park called Seaton Park.

By 1950 the atomic bomb had changed every assumption about air defence, and a programme codenamed ROTOR replaced the surface radar stations of the Second World War with hardened underground operations rooms. Boulmer's bunker, designated an R3, was a two-level facility designed not to survive a direct nuclear hit - nothing of its scale could - but to take a near miss from a 2,200-pound armour-piercing high-explosive bomb dropped from 35,000 feet. It became fully operational in September 1954. The bunker was upgraded to an R3A standard in 1982, modernised again in 2002 under the sixty-million-pound UKADGE Capability Maintenance Programme, and is now the home of the UK's Control and Reporting Centre, callsign Hotspur, tasked with compiling the Recognised Air Picture across NATO Air Policing Area 1.

For decades, RAF Boulmer's most visible role was search and rescue. A Flight of No. 202 Squadron flew the bright yellow Westland Sea King HAR.3 from the base, providing twenty-four-hour rescue cover from Fife in the north to Hartlepool in the south, reaching west across the Lake District. The Sea Kings answered everything: fishing boats foundering in the North Sea, climbers stranded on Helvellyn, walkers caught out in the Cheviots, light aircraft down in remote glens. On 30 September 2015 the last Sea King lifted off from Boulmer and the RAF's role in UK civilian search and rescue ended. The mission was transferred to HM Coastguard, contracted to Bristow Helicopters flying newer Sikorsky S-92 and AgustaWestland AW189 aircraft. Locals along the Northumberland coast still talk about the yellow helicopters as if they had only just left.

Today RAF Boulmer is the operational headquarters of the UK's Air Surveillance and Control System. The Air Command and Control Force here directs Britain's Quick Reaction Alert fighters - the Typhoons that scramble from RAF Lossiemouth and RAF Coningsby to intercept unidentified aircraft entering UK airspace. Between 2005 and 2016, according to figures in The Daily Telegraph, there were 187 such interceptions. The remote radar heads that feed Boulmer's picture span the country: Saxa Vord in Shetland, Benbecula in the Outer Hebrides, Buchan in Aberdeenshire, Brizlee Wood in Northumberland just up the road, Neatishead in Norfolk, Portreath in Cornwall, Staxton Wold in North Yorkshire. Every flight that crosses British airspace, civil or military, registers somewhere on a screen at Boulmer. The plywood Hurricanes of 1940 have become the eyes of NATO.