I think that the black box is for keeping the bin bags dry whenever the driver decided to leave the NA hood at home. The N Type hoods are very bulky items !
On a more serious note Chris, whilst I agree that the picture of AYT197 on Nailsworth Ladder is excellent, and one I have not seen before. the caption is wrong/ . That section is not Nailsworth, - it is Mill Lane at Prestbury, near Cheltenham.
This is not the first "trials howler" committed by the editorial team at The Sports Car Magazine.
Thanks, Brian, good point although I cannot remember seeing any other car displaying one of these. At the moment that seems to be the best explanation.
Thanks, Colin for your encyclopaedic knowledge coming into play once again ! I will amend my records accordingly. I am looking out for a June, 1935 copy of The Sports Car magazine if anyone has one for sale.