Complex sentence: No provision had been made for deep wading trunking and the A30 was unable to participate in the Normandy landings; the tank had to wait until ports had been secured and the Mulberry harbours completed.
Split into simpler sentences: No provision had been made for deep wading trunking and the A30 was unable to participate in the Normandy landings. Challenger crews had to wait until ports had been secured and the Mulberry harbours completed.