Network Rail is having to spend millions of pounds digging up parts of the recently revamped London Bridge station after discovering a number of water leaks.
New Civil Engineer first reported that retrofit waterproofings are now being carried out at the station despite the £1bn upgrade that was officially unveiled by the Duke of Cambridge in May.
Network Rail said water sources outside of the station which were not listed on historic plans of the station were to blame.
The £1bn upgrade involved the opening of five new platforms, almost doubling the station's passenger capacity from 50m to 96m people a year, in what Network Rail said was a "shining example" of investment.
A Network Rail spokesperson said: “While substantially complete and fully open to passengers since January, London Bridge station is currently undergoing a series of finalisation works including waterproofing in some areas.
"The works will be completed within the target cost of the £1bn transformation project which has created a modern transport hub capable of accommodating nearly twice the number of passengers than previously to more destinations than ever before.”
As well as the station upgrade, Network Rail also has plans to nearly double the number of Thameslink trains running through London. However, the new timetable of up to 24 trains per hour at peak times has been delayed until December 2019, with the spending watchdog finding problems with the Department for Transport and Network Rail's planning ahead of the launch.