If it is true, that the BA flight landed with a total of 5 tons remaining fuel onboard, of whitch only 2 tons was usable, I certainly see why the crew stated, that a go around was ruled out.
As far as I remember, we used 200KG/MIN as a rough figure for FF in landing configuration on the -400.
Landing with less than 10 tons of fuel onboard would trigger a voyage report as well!
The decision to continue the flight on three engines, given the very few "facts" available so far, sounds safe, and completely in line with SOP
s for that A/C type, however landing with 2 tons usable fuel, could/should have concerned the crew prior MAN.
Bearcat - exactly my thoughts!