SR - yes, that was also BA's 'approved procedure' when I left in 2004 - using LHR as a second runway for LGW and allowing crews to burn down to land with 'E' ('final reserve') fuel as long as:
Wx ok
EAT known
No plausible failures of ground equipment which might preclude a landing at LGW.
Inumerable bright young cadet 'CEO of the future' co-pilots tried to persuade me to do this as I started to mumble into my beard about diverting, until I made them look at the arrival fuel at LHR if you then went round at 3 miles with a blocked runway at LGW, when they went quiet - it was just about enough to cover the fuel pumps. It was indeed item 3 that bothered me at LGW, and I never got an answer from the 'dreamer's in BA as to whether they considered a runway to be necessary ground equipment
. The point of my 'Edit' was to point out that telling LGW ATC that you are 'committed' meant nothing OFFICIALLY to them (and that when they found out what it meant they might think you should be
). The runway did not become 'yours' and life went on as normal from the time you 'committed' to the time you landed.
EDIT: To add - I'm not aware of VA's policy on this. You never know, the crew could have been planning on LHR, to be told by OPS there was no way due to manpower or whatever, and it has not been unknown for a crew (NB not VA before I am leapt on!) to do this to highlight an issue.