HS2 was supposed to give us high speed trains linking London with Birmingham and Manchester, freeing up the clogged West Coast Main Line and forming the critical first part of a network reaching as far north as Leeds.

But in late May, the Government announced costs had ballooned from the £32bn originally quoted in 2011 to more than £100bn. The first trains were supposed to head north in December this year; now they are not expected until 2036 at the earliest, and will have to run more slowly than planned. The spurs to Manchester and Leeds have been long since scrapped.

It’s a fiasco. So who and what is to blame? Journalist and author Sally Gimson, transport writer Christian Wolmar and former HS2 technical director Prof Andrew McNaughton give their perspectives.

Bat tunnels, a northern leg cancelled by a prime minister while speaking in the city the newly cancelled leg was supposed to serve, £600m of land bought which will now not be needed for the railway, high speed trains which ministers have decided can’t run at high speed, endless delays, and an overall price tag of £100bn.

We all know by now the increasingly absurd ways HS2 has gone wrong. So rather than simply listing the numerous errors made by those who conceived and are building HS2, it is instructive to look at how other countries got it right.