There used to be , and may still be a restored painted cannon barrel mounted muzzle up in a grass patch outside the cabbie canteen in the cab waiting area , and across the road from the LHR cop shop .
Reliably , reputed to be where Princess Elizebeth ascended her throne , with her 1st step back onto UK soil , alighting there from the Argonaut .
Equally learned today that the fire dump Argo. was not her a/c.
My LHR years encompassed taxi clearance from the Outer to the Inner via [ in turn ] ' Argonaut Arc , Comet Corner , and Trident Turn ' . Never taxied by the JGG , or otherwise the Boelas / Douging 710/107 ... But could see the steel rusting far quicker than real a/c aged .
rgds condor .