Hi Gavin,
The handle is to pull open the wheel carrier and keep your hand away from the likelihood of chopping off your fingers. The trigger on the handle catches into the extension with the hole visible beside the tyre to lock the door/carrier assembly open particularly on a side-slope. The handle is angled to the left to maintain clearance to the wheel as the carrier opens to the lock position.
Designed in 1970 in its earliest versions for Series vehicles;). Series ones have the tyre slightly further to the right.
Bob

