It was not just the searing heat of the day, which was hot enough to boil an egg on the bonnet of a lorry, or the sand that nestled in every crevice of the body, or the shivering cold of the starlit nights, that the British and Commonwealth troops had to battle in the North African desert – it was also the tough and determined Axis forces, often under the command of their brilliant leader, Erwin Rommel.