General Wavell realized on April 3rd, 1941, that Rommel was energetic enough that he might end up in Egypt, unless Wavell put together a defensive front to stop him. This was they day he flew back from Cyrenaica. He would have liked to use the experienced 4th Indian Division, but they were engaged in East Africa. All he had was the 7th Australian Division and part of the 6th Division. The 7th Australian Division had been intended for Greece, so using it meant landing troops in the Dodecanese. The Chiefs of Staff in Britain agreed with the move.
Anthony Eden and General Dill were in Cairo on April 6th, and they apparently conferred with Wavell, Admiral Cunningham, and Air Marshall Sir Arthur Longmore. They hoped to be able to hold the Germans at Tobruk. They 18th Australian Brigade was still at sea, on this date, headed for Tobruk. The 22nd Guards Brigade, from the 6th Division, was advancing towards Bardia. Two of the three 11th Hussars squadrons were driving up the coast road. Sir Arthur Longmore decided that he needed to reestablish the airfields east of Mersa Matruh, with the aim of having safe fields from which to operate to be able to harras the enemy and protect the troops.
This is based on the account in Vol.II of the Official History.