A key London Underground section has been reopened following a 17-week closure for major improvement work.
A new, wider southbound platform was also opened as part of work to boost the station’s capacity by 40%.
Once the project is completed later this year, the station will have step-free access to the Northern line, improved access to the Docklands Light Railway, two new moving walkways, 12 new escalators and two new lifts.
There will also be more direct routes within the station and a new entrance on Cannon Street.
The resumption of full Northern line services comes a week before the Elizabeth line opens following the completion of the Crossrail project.
On a visit to Bank station, Mr Khan said: “Today marks the first in a series of transport milestones for our city.
“The Northern line has fully reopened to customers, on schedule and to budget, after the successful completion of the latest phase of vital upgrade works at Bank station.
“Bank station is at the heart of the city and these improvements are the first step towards a modern, accessible, easy to navigate station fit for the 21st century.”
He added: “This is one of the most complicated underground stations in the world and it’s really good to see the improvements because of our investment.”
Stuart Harvey, chief capital officer at Transport for London, said: “The old layout was very constrained, leading to frequent congestion, but Northern line customers will now be able to make their journeys much more quickly and easily.
“I’d like to thank our customers for their patience while the Bank branch of the Northern line was closed, which was essential in enabling us to complete this work.”