It's hard to doubt that LBA-LHR will be a success
Actually, I wasn't expecting to see any of the shorter routes coming back, given how LHR charges / APD / faster train services kill most of the centre to centre market, and that Leeds is still not Manchester.
So in that respect, well done BA, good luck with the new route, may it be a great success.
The other thing with LBA is that it is a busy enough airport, but few feeders into other hubs - no AF / CDG, no LH / FRA. How much business demand is there for the M4 corridor area ex LBA? That is where the train is rubbish.
Again, we can only speculate on future infrastructure, but with a 3rd, short runway at LHR, then maybe CAX would be one to consider - but still long after INV / NQY etc.
So DND could take a 318 or E70/95? Given the existing LCY route, would BA move around a/c just to serve this and maybe one or two other places (GCI)?