A brief history of the Battle of Crete has been posted on a military history weblog. In it there is a brief mention of Waugh and his Commando unit in action. This occurs near the end of the battle:

After a day’s fierce fighting, Laycock decided to retreat under cover of night to nearby Beritiana. He was joined there by Captain Royal and the Māoris, who took up separate defensive positions and eventually made their fighting retreat. Laycock and his force, however, were cut off by superior German forces near the village of Babali Khani (Agioi Pandes). Pummelled from the air by dive bombers, Layforce Detachment was unable to get away. Laycock and his brigade major, the novelist Evelyn Waugh, were able to escape by crashing through German lines in a tank. Most of the other men of the detachment and their comrades from the 20th were either killed or captured. By the end of the operation about 600 of the 800 commandos sent to Crete were listed as killed, wounded or missing. Only 23 officers and 156 others managed to get off the island.

The account of Waugh making a break through enemy lines in a tank was something he had not mentioned in his war diary nor is Guy Crouchback involved in any such action in the fictional version. Waugh does describe in his war diary the use of a tank by men of his unit but he did not participate:

In an arbour of sweet jasmine I found Bob and Freddy and two brigadiers; they had had an adventure, being attacked at close quarters by tommmy-gunners. Bob had jumped into a tank and Ken Wiley, second-in-command of A Battalion redeemed the Commandos’ honour by leading a vigorous and successful counter-attack. A few New Zealanders, mostly Maoris, had rallied and were joining us in the rearguard.

Bob is Robert Laycock, commander of the Commando, and Freddy is F.C.C. Graham, then Laycock’s brigade major. Waugh was the intelligence officer, not brigade major as described in the Weblog, so the confusion may explain how Waugh was thought to have been in the tank. In his diary account, Waugh learns of this tank “adventure” shortly after his discovery of the dead British soldier in the churchyard. Afterwards, Waugh describes how he, Laycock and Graham drove in a truck back to the place where Waugh had left “Major Hound” cowering in a drain: “Bob as politely as possible relieved him of command saying ‘You’re done up. Ken will take over from you.'” According to the diary, this all took place near the village of Babali Hani (called by Waugh “Babali Inn”) (Diaries, p. 504).

Antony Beevor in his Crete: The Battle and the Resistance (p. 203, 2005), describes the involvement of two Matilda tanks which arrived from Heraklion just in time to save Laycock and Graham (but no mention of Waugh). This incident took place when German mountain troops cut the road between Stylos and Babali Hani. Although Beevor doesn’t mention a “break” through German lines, that would appear to be what happened after the tanks arrived. The incident, according to Beevor, helped “to stiffen the resistance at Babali Hani” where Laycock set up his brigade headquarters. It was apparently there that Waugh joined them (according to his diary) coming from the other direction.

There seems to be no counterpart of the tank “adventure” in Officers and Gentlemen, at least not in that part of the narrative that follows Guy’s discovery of the dead soldier (Penguin, pp. 206-12). In the novel, Guy finds himself among his old comrades from the Halberdiers and is rejoined by the Commandos who proceeded along the road from the German lines accompanied by some New Zealanders.

Thanks to Prof. Donat Gallagher for pointing out the diary entry where Waugh mentions the tank encounter.