We seem to stumble through many similar projects. The background to many seems to me to be pushed by lobby groups with vested interests and using forecasts that would stand out in the fiction/comedy section.
So a massive cost will save 20 mins on the travel time for limited numbers of passengers. Tickets at a premium? Whoopee-doo!
I could understand Concorde up to a point as it enabled big time saving for a long journey but even so it was expensive. A great example of national prestigetoo, BUT
Meanwhile those on the route will be upended and blighted, the building companies will earn ££££££, Politicians, of course( !) will not benefit in any way.

When ESSENTIAL sectors are starved of money this project is obscene.
Wilson cancelled TSR2 due to cost so a precedent is there.
The Welsh Assembly wasted £9M on the Circuit of Wales and we’re highly criticised by the watchdogs. The “backer” was of dubious intent and money not wisely used ( edited comment).
The political industry is alive and well in Westminster. Lobbyists prevail.