Complex sentence: On 17 November 1941, the day of the raid, Rommel was not in North Africa, having left for Rome on 1 November, which was known to British military intelligence via an Enigma intercept.
Split into simpler sentences: On 17 November 1941, the day the raid took place, Rommel was not in North Africa. He had left the operational area for Rome on 1 November-a fact known to British military intelligence via an Enigma intercept.