A new Underground ticket hall opened at King's Cross this weekend, having survived a rocky few years of development. At one point the Department for Transport almost killed the scheme.

The Northern ticket hall is the last piece in the Underground jigsaw at the King's Cross/St Pancras hub, and will double the size of ticket hall space below ground. 

There will now be three ticket halls serving the numerous Underground lines. The other two are the Tube ticket hall – for the Piccadilly, Victoria and Northern Lines – and the Western ticket hall, for the Circle and other subsurface services. Both of these have been open for two years or more.

The Northern ticket hall will provide more convenient access to the deep tube lines from St Pancras in particular, but this part of the scheme was almost killed in 2004, as costs soared. While work on the other Underground developments continued, construction of the Northern hall was suspended on the orders of the DfT, which was concerned about the rising price tag. When it reached £250m the Department took action, and the worksite was sealed off for two years, while references to the project were removed from hoardings around the stations.

However, after tense negotiations between the Department and the Mayor of London, the scheme was recosted in connection with Network Rail work on the ground above, where a new western concourse is being built for King's Cross main line station, and a maximum combined price of £400m was agreed for both projects. Approval to restart was given in 2005, and work on the ticket hall was resumed in spring 2006.

The 2000 square metre hall is linked to 300 metres of new tunnels which lead to the trains. It has ten escalators and six lifts, although step-free access to the Northern Line will not be available until mid-2010, said TfL.

Transport secretary Andrew Adonis appeared to be putting the project's chequered development history behind him, when he said: "This project demonstrates our firm commitment to delivering a sustainable and efficient transport system fit for the 21st century."

The new hall was formally opened on Saturday, and opened to the public on Sunday. The project has still run slightly behind its revised schedule: the 2006 construction plan had envisaged completion in September this year.