Plans to expand the capacity of the maze that is Bank tube station have been approved by TfL. The upgrade, which will cost £563 million will see the capacity of the tube station increased by 40%, and two news travolators added to speed transfers between the Central and Northern lines.

However, it will take until 2021 for all the works to be completed, and part of that will see a partial shut-down of the Northern Line for two months in 2020.

The main gist of the plans is to dig an entirely new southbound tunnel and platforms for the Northern Line, then create a much larger set of corridors linking the Northern Line platforms to the rest of the station.

The new corridor will in fact be the old Southern tunnel, in a reuse policy that worked well at stations such as Euston, Angel and London Bridge.

There will also be a new entrance to the station built on Cannon Street, roughly half-way between the two existing entrances to the Bank-Monument complex of tunnels.

And to finish off, three new lifts and 12 new escalators are being included.

The redevelopment will complement current work to create a new entrance to the Waterloo & City line. Just metres away from Walbrook Square, the new entrance will offer two new lifts, four new escalators and a new ticket hall when it opens in late 2017.

Once work starts, over 200 engineers and staff will work on site at Bank 24-hours-a-day until 2021.

Most of the tunneling will be by mechanical diggers and sprayed concrete — the site is too small and complex for a big sexy tunnel boring machine to work in.

The main construction works are expected to finish around April 2020. Then the Northern Line closes for a couple of months, and the new underground tunnels should be ready for the public in August 2020.

It’ll take another year to build the new entrance on Cannon Street, as that would have been a building site until then.

Works should start early next year.