On 30 August the Germans had made their biggest effort since the mass onslaught on 15 August, but the very next day a still larger operation was mounted by the Luftwaffe. Fighting was to be heavy and costly for both sides. Fighter Command's losses were the heaviest of the whole battle, 39 aircraft shot down with 14 pilots killed.
Action was joined at 8.00am as four waves totalling 200 aircraft came in over Kent and the Thames Estuary. North Weald, Debden and Duxford airfields were the targets. The raid heading for Duxford was intercepted before it could reach its objective, but a force of Dornier 17s slipped through the defences to drop about 100 bombs on Debden, the most northerly sector station in 11 Group. Casualties were incurred and some aircraft and buildings were destroyed but the airfield remained open. An hour later, Eastchurch suffered limited bomb damage to its airfield and buildings.
The next attack, which began shortly after noon, was the most serious of the day. Over 100 aircraft crossed the coast at Dungeness, one section headed for Croydon and Biggin Hill airfields, the other for Hornchurch. At Croydon one hangar was demolished and other buildings damaged. At Biggin Hill, two of the three remaining hangars were extensively damaged and the operations room took a direct hit. The temporary telephone lines and electricity cables installed after the previous day's raid were destroyed. At Hornchurch some aircraft were damaged while taking off but the airfield remained serviceable despite some cratering.
At 5.30pm, Hornchurch and Biggin Hill were attacked again. The former had its runways and perimeter tracks bombed for the second time. Both aerodromes were serviceable the following day. However, at Biggin Hill, coupled with the effects of the attacks on 30 August, the situation forced the withdrawal of two of the three squadrons based on this airfield to be put under the control of adjacent sectors for more than a week afterwards. Biggin Hill received its sixth raid in three days on 1 September and was bombed again on 5 September.
Blenheim – 54
Spitfire – 212
Hurricane – 417
Defiant – 13
Gladiator – 4