Boris Johnson announced on Tuesday that the High Speed 2 (HS2) rail line will indeed go ahead after months of debate. The first phase, between London and Birmingham, will be completed between 2028 and 2031, whilst the second phase extending to Leeds and Manchester is due to finish by 2040, according to the Department for Transport (DfT).

HS2 will enable trains to travel at speeds above 200mph, with 18 services to and from London using the line per hour. According to DfT figures, it is projected to reduce journey times between London and Birmingham from 1 hour and 21 minutes to 52 minutes. Supporters also claim it will help create jobs and help release capacity on the West Coast, East Coast, and Midland main lines.

HS2 was initially announced in 2010 by then-Transport Secretary Lord Adonis and projected to cost £30 billion. Since then, the scheme has seen revisions, parliamentary scrutiny, delays, and cost overruns. Whilst the 2015 Budget projected a cost of £55.7 billion, the HS2 chairman admitted this was unrealistic, with one independent projection estimating the price tag ballooning to as high as £106 billion. Experts blame the spiralling costs on the price of compulsory purchase orders for property, moving and rebuilding of infrastructure to make way for the line, and the lack of realisation of efficiency savings that were projected in earlier budgets.

In his statement to parliament, Johnson admitted that “it has been a controversial and difficult decision”. Criticising HS2 Ltd.’s management of the project, he said that whilst “cost forecasts have exploded”, it did not detract from the “fundamental value of the project” and that action would be taken to “restore discipline to the programme”.

Labour leader Jeremy Corbyn criticised the “abject failure” of Conservative governments since 2010 to keep costs under control. He claimed this was the reason “that the project’s future was in any doubt”. Corbyn supports the completion of the rail line as “a means to boost regional economies and slash climate emissions” which will “(free) up other lines”.

Opponents claim that asides from its high cost, the scheme would also cause environmental harm, and that compulsory purchase of land would force people out of their homes. Green Party MP and former party leader Caroline Lucas, who has called HS2 a ‘vanity project’, said that it would “destroy or damage hundreds of important wildlife sites, areas of ancient woodland and local nature reserves”.

Victoria Prentus, Conservative MP for Banbury in North Oxfordshire, said it was a “sad day”. Prentus has earlier called HS2 a “train wreck” of a project and is “concerned by the environmental impact of HS2, and by the financial and governance issues of this project which have become increasingly worrying”. Prentus nonetheless accepted that the “project is to go ahead, and it must be a success” – for which plans must be “re-worked as necessary”.

Both Oxford East Labour MP Anneliese Dodds, and Oxford West and Abingdon Liberal Democrat MP Layla Moran, have been absent from HS2 votes held during their time in parliament.