By Sarah Mukherjee
BBC environment correspondent
It might seem like a rather strange place for a public inquiry.
Could the tidal Thames solve London's water supply problems?
The gleaming steel, glass and chrome of London's City Airport, with small planes leaving and arriving regularly, would not seem the obvious point from which to start a discussion about the future water requirements of millions of Thames Water customers.
But the evidence of how close this is as a subject is all around you.
Look past the fluttering flags of the many countries London City Airport serves and you see what everybody here is talking about. Water.
In particular, brackish, slightly salty Thames water - tidal Thames water - that the company Thames Water says it can turn into fresh drinking water at the rate of 140 million litres a day.
'Demand too high'
The desalination plant itself is planned for not very far from here either.
Look down the river beyond the futuristic housing developments and the giant wind turbines on top of the Dagenham car factory, and you can just see where the site should be.
Thames Water says without approval for this project it will be unable to supply the increasingly voracious demand of its eight million water customers as the years progress.
They say there simply are not enough supplies at the moment to go round.
The water source for the desalination plant, however, is, in theory, infinite.
Thames Water says demand in London will outstrip current supplies
But this is a very controversial plan. Although it was originally approved by Newham Council, the local planning authority, the mayor of London is opposing it vigorously.
He is in charge of the London plan and has overall planning control and he directed the local authority that it could not approve the scheme.
The mayor objects for two reasons. Firstly he is concerned about the energy that this desalination plant would use.
The increase in carbon dioxide emissions - one of the gasses scientists believe is contributing to global warming - does not sit well with the mayor's avowed intention of reducing greenhouse gas emissions across the capital.
One of his advisers has described the scheme as "pouring oil on the fire" of global warming.
The second is the question of leakage. The mayor says 10,500 litres of water are lost through Thames Water's leaky pipes every second - and it should be spending the proposed £200m for this new project on fixing those.
But for Thames it is not an either or. It says that even with increased water efficiency, managing demand and fixing the pipes as quickly as it can, it will still not be able to meet the demand in the future.
This could lead, it says, to severe water shortages in the medium term, possibly even stand pipes, and what they have described as a potentially catastrophic social and economic consequence for London.
Although this is very much a London issue at present, it has national and even international implications.
Other water companies are looking at this public inquiry with interest.
The way the planning inspector and indeed the ministers decide will give, they say, some indication of how likely or unlikely they might be to get approval for desalination plants in other parts of the UK.
And it has even generated international interest from green groups around the world.
The mayor says he has received messages of support from as far afield as California.
This London issue could, both parties think, set a precedent for what will happen in other parts of the UK as water shortages become a possibility or even a reality.