And yet it all went pear shaped. That's the intriguing bit - how and why it went so badly after it went through readiness reviews.
I think that highlights a problem which isnt confined to the rail industry. Any review is only as good as the input information, and unless there is someone genuinely independent to ask awkward questions it will end up being a rubber stamping exercise.
The industry I work in has had some major safety challenges in the past, and one of the internal findings was that a fully independant person(s) should always be part of any review (in this case when plant changes were being considered), and that the independant person(s) should have good experience of the principles under discussion and be confident (translation 'an awkward old...') as this was the only way that errors and sometimes fundemental flaws in any proposals will be uncovered.
OK so timetable changes probably do not carry direct safety risks, but getting them wrong has a huge impact, so independant review would be needed. Going back to the May 2018 meltdown there were 'schoolboy errors' in the proposals which everyone could see, but somehow they got through. A local example: 2 trains, from opposite directions calling at the single platform at Malton with in 3 minutes of each other.