en:British anti-invasion preparations of World War II Pillboxes possible invasion of the British Isles WW2 anti-tank blocks (en) Pillboxes World War Two defences British anti-invasion preparations They sure did at the time World War Two defences en:British anti-invasion preparations of World War II British anti-invasion preparations World War Two defences British anti-invasion preparations anti-invasion measures British anti-invasion preparations defence of Britain possible invasion of the British Isles British anti-invasion preparations of World War II