The navy started the fight to defend Crete at a disadvantage, as the aircraft carrier Formidable was unable to participate, as after the Tiger Convoy, her fighter strength was reduced to four. Suda Bay was no longer usable, so the fleet had to return to Alexandria to restock with ammunition and to refuel. There were only some motor torpedo boats based there.
Admiral Cunningham's plan was to interdict traffic by sea at night and to withdraw to the south during daylight hours. He had assembled three groups of cruisers and destroyers, augmented by the MTB's from Suda Bay.
The Corinth Canal was mined to impede traffic flow, and this was successful.
At the start of 20 May 1941, Rear-Admiral Rawlings, in the Warspite and with the Valiant were to the west of Crete. They had a screen of 10 destroyers. The Naiad and Perth, with four destroyers were heading south from Kaso Strait. The Dido, Ajax, and Orion, with four destroyers were heading to join Rear-Admiral Rawlings from Antikithera Channel. The cruisers Gloucester and Fiji had left Alexandria, heading to join the battlefleet, as well. The Queen Elizabeth and Barham had returned to Alexandria after the Warspite and Valiant had arrived.
This is based on the account in Vol.II of the Official History