The British tried to keep from having to remove the rest of the Australians from Tobruk in September 1941

Upon the completion of Operation Supercharge, there were still two Australian brigades left in Tobruk. Churchill, in particular, wanted to not withdraw the brigades, at least not prior to Operation Crusader. The last two Australian brigades fully expected to be withdrawn during the next moonless periods. The British 16th Brigade had arrived and advance group from the 6th Division headquarters were in place in Tobruk. The British units were already being familiarized with the ground that they would defend. The British soldiers met the Australians and socialized with them.
Churchill and his military leadership planned to complain about the impact of the further withdrawal on Operation Crusader. Churchill was always optimistic about the possibilities for future operations. He could visualize announcing in Parliament that the new 8th Army had pushed through and relieved Tobruk and had destroyed the enemy armored forces on the way.That vision seemed much more important than the Australian government's insistence that the division that had been in Tobruk for about six months needed to be withdrawn.
The British thought that they could plead that establishing an ascendancy in the air over the Axis air forces would be compromised by having to provide air cover for the final Australian removal from  Tobruk. The unmentioned reason for the British low capability in the air was that they were still unwilling to send Spitfires to the Middle East. That left the RAF in North Africa with Hurricanes and Tomahawks, which were outclassed by Bf-109 fighters.
The truth was that despite having to provide air cover for the relief convoys removing Australians from Tobruk, They already were committed to provide air cover for the regular supply convoys. These were mainly carried in destroyers which had a limited capacity for cargo. To unload at the Tobruk harbor, some ships were moored to jetties while others were tied up to sunken ships and others were simply anchored while lighters moved the cargo ashore.
Air Marshal Tedder wrote a message to the Chief of the Air Staff. The gist of the message that if the enemy continued to refrain from attacks on shipping, the continued relief could proceed without having a great impact. If they did decide to attack the convoys, then the burden on the RAF would greatly increase due to the continued removal of the Australians from Tobruk. This is based on the account in Vol. III of the Australian Official History.