Diversions
One could say that there should be a certain quid pro quo within the industry to accept as well as to expect receipt elsewhere of diverted flights when circumstances dictate. This however requires the support of many stakeholders, not just the airport operators.
I think it is a measure of an airport's maturity when inbound diversions cease to be a big deal and a notable business consideration. I can't imagine that anyone at Heathrow gets excited about them. Manchester should have passed that point some years ago, even if not all of its aficionados have got there yet.