The Battle of Britain Five Months That Changed History, May—October 1940 by James Holland (z-lib.org).epub

Park had sensed something was up; the invasion talk and the promise of
good weather had made it inevitable. He had even forgotten his wife’s
birthday that morning, although she had assured him that a good bag of
German aircraft would be present enough. Over breakfast at Chequers, the
Prime Minister had also had a feeling the weather would be good for the
enemy, so with his wife, Clemmie, and bodyguard in tow drove to 11 Group
Headquarters. There, he assured Park, he had no wish to disturb any station
but Uxbridge, and had called by on the off chance that something was up.
Park led him to the underground Operations Room, a bunker a couple of
hundred yards from the main Headquarters in Hillingdon House. Painted
green with a lead roof, it was an unprepossessing and shallow block,
offering a tiny target from the air. Steps led down to the entrance, a latticed
iron gate, which then opened the way to a longer set of steps going down
some thirty feet, the air conditioning system whirring loudly overhead. As
the steps turned sharp left and descended another thirty feet, Park tried
tactfully to explain that the underground air conditioning could not really
cope with cigar smoke.
They continued down a long corridor, lined with thick, rubber-coated
wiring, then Park took the Prime Minister up a short staircase into the
viewing room. There, through a screen of curved glass designed to reduce
the glare and reflection and to cut out the sound from those below,
Churchill looked down on the Operations Room with its map table, tote
board, clocks, WAAF plotters and Ops staff. The viewing gallery was quiet
save for the now soft, background whistle of the bunker’s ventilation
system
As it happened, he had arrived just in time. Churchill and his wife – he
with an unlit cigar clenched between his teeth – stood watching the plots
being shuffled across the plotting table, and, along the tote board, the lights
being lit up as squadrons took to the air, and then turning from the four
colours of their sections to all red as they engaged.
‘Hello, Gannic Leader! Gannic Leader!’ Tony Bartley now heard in his
headset. ‘Carfax calling! Two hundred plus coming in over Red Queen.
Vector 120, angels 22.’
‘Hello, Carfax, Gannic Leader,’ Tony heard Brian Kingcombe reply.
‘Message received. Over.’