I'm saying we arrived at LHR with ample holding fuel but an unforecast wx change led to extended holding and creeping EATs beyond the point at which we had committed to LHR. We were then left with the choice of diverting to LTN (single runway) or remaining in the hold for LHR (dual runway). Overall we decided the far safer option was to remain with two bits of tarmac to land on than one, as did the many other aircraft which landed in a similar state at LHR that night. Had we decided en masse to divert to Luton and Stansted you'd have found a whole load of fuel emergencies all waiting to land at single runway airports with no room for error in the event of a single runway closure.
If it all went tits up at LHR we could use the other main runway after a go around or R23, and in extremis Farnborough or Biggin Hill were available. After a diversion we'd have had nothing but Luton or at a push Stansted by eating into reserves. I'd rather stick with 4 runways in close proximity than 2 runways at busy single runway airports.
The CAA had a good look at the events of that particular evening and concluded that everybody had worked to the rules in what were difficult and unexpected cirumstances.