I was in charnock many years ago (sixties)one night and got talking to a young lad who new it all type,and he was adamant he had a sleeper cab on his Thames trader I just nodded my head and put it down a rich imagination,I finished my meal and we left,when we got outside low and behold he had a trader,the sleeper on the back(I can’t type for laughing)was about eighteen inches high with a tarry felt roof,the sides were made of old pallets (fifteen inches)high vertical slats,when he switch on his cab light it looked like a cage(I am still laughing)