Kit Malthouse points out that if the Hyde Park interchange was to go below ground then “the three great parks of Central London could be united. You could walk from Parliament Square to Queensway, about three miles, without crossing a road. Park Lane would be freed up for redevelopment, and a grand new public square could be created at Marble Arch.”
My reservation is that we don’t do big projects particularly well in this country and it is all too easy to imagine this turning into some kind of British big dig and bringing London to a total standstill. But if it could be done right, it would certainly be worth doing.