825 Squadron Fleet Air Arm in January 1940, which was equipped with Fairey Swordfish aircraft.
Buckley was awarded the Distinguished Service Cross in July 1940 for "daring, endurance and resource in the conduct of hazardous and successful operations by the Fleet Air Arm working with the Coastal Command in France and over the Channel".
All the recaptured escapers, including Buckley, Bushell and Day, following a brief period in solitary confinement, were transferred to Stalag Luft I at Barth.
At Stalag Luft I, Day again assumed the role of senior British officer, and again appointed Buckley as head of the escape committee.
The compound at Barth was becoming overcrowded and, due to the number of escape attempts being made, the German authorities, under directions from Reichsmarschall Hermann Göring, decided to transfer all air force prisoners to a newly built camp at Sagan.
To improve security and provide anonymity from the Germans, Buckley became known as 'Big X' – a term later made famous by its use by Roger Bushell and the character based on him, played by Richard Attenborough in the film, The Great Escape.
By October 1942, the compound at Stalag Luft III was becoming overcrowded, and the Germans transferred a number of officers to Oflag XXI-B at Schubin in northern Poland.
The camp at Schubin was administered by the German Army (the Wehrmacht), and had recently held French POWs.
Following a disagreement between the camp commandant and Day (the senior British officer) over camp conditions, Day instigated several tunnel schemes by which a mass escape attempt could be made, with the sole objective of having the commandant removed by the German authorities for failing to prevent a mass break out.
Buckley, with 34 others (including Day, future MP and journalist Aidan Crawley, journalist/author Robert Kee, German-Jewish RAF pilot Peter Stevens and future Chancellor of the Exchequer Anthony Barber) crawled through the 150 ft tunnel, which started from the camp Abort (toilet block).
Buckley and Thalbitzer are known to have travelled to Copenhagen before attempting a crossing by canoe to neutral Sweden.