To say Willie Walsh is against expansion at LHR isn't entirely true:
https://www.theguardian.com/uk-news/...h-third-runway
BA and IAG are happy for LHR to expand as long as the cost is reasonable - clearly WW thinks Heathrow Hubs plans offer an acceptable cost.
Regardless of what WW thinks, should we let the dominate carrier at LHR dictate the market there. I'm sure many other airlines (both current and potential future users after expansion) would be happy to pay the cost of expansion if it meant increasing their flights there. The CEO of LHR has often stated he has 30 airlines wanting to set up new routes or increase frequencies on current ones.