Remember that part of the design mission is zero carbon emissions.
That means LH2 (liquid hydrogen) fuel.
Hydrogen is not a zero emissions fuel.
In fact, the standard hydrogen car outputs much more CO2 than my diesel car. The hydrogen has to be generated via grid electricity or the gas reduction process, which outputs a lot of emissions. And since there are so many losses on the cooling and storage of hydrogen, the hydrogen 'battery' is a very inefficient one.
London Transport had three hydrogen buses, that they championed as being 'emissions free'. But after prompting and getting a FoI request, it turned out that the hydrogen generator was in the London Docklands. So all they were doing, is taking the emissions out of Central London, and spraying them all over the people living in the East End.
Charming.