SUCCESS!
So as suggested above, the locking cap is supposed to prevent access to the hex bolt in the picture and there by prevent you from undoing the clamps……
Except clearly the caps are miles away from the hex bolt and you can reach the hex bolt with a basic allen key to undo the clamp, which i’ve just managed to do – fiddly but do able and no damage to the bars.
You would need a ridiculously long allen key access from the end that the cap covers in this case but i suspect is fortunate that the bars the clamps attach to are quite inset on the canopy compared to the full width of the roof.
Cheers for your help everyone!