That London City self promotion is slightly disingenuous in the fact that technically London City doesn't serve JFK directly, which is the inference, they do fly to Shannon though where the aircraft can actually depart with the fuel load it needs to cross the pond.
....and with its pax already cleared for USA border control and customs, making a New York arrival "a walk in the park". BTW, the eastbound flight is nonstop.
The land is an asset but the airport is a liability. The company is known as a builder and not an airport operator so the writing was on the wall they day they got their hands on the airports land bank.
Some sort of airport facility is required for the Irish Sea gas and oil industry in the future (oil prices will rise again, it's cyclical) and for the fracking industry which eventually will get the go ahead as the UK needs "energy security". Overseas suppliers are seen as "too unreliable".
That will probably generate pax business as well is the case with Aberdeen. So clearly, it's common sense to safeguard the rwy area and parts of the airport. If all 400 acres is not needed for aviation, some land can be released for other uses, but it is necessary not to go overboard and ensure that enough land is retained for future airport expansion (for infrastructure, not another rwy!).