The Northern Line - often dubbed the 'misery line' - will not be running to its full potential until 2011 at the earliest, an Underground contract manager admitted last week.
Weekend closures on the High Barnet branch for engineering work - in place over the summer and continuing this weekend - are almost certain to return early next year, according to Lee Jones, the Northern Line infrastructure manager for Tube Lines, the firm responsible for maintenance of the line.
Tube Lines has committed £600 million to installing a new signalling system on the Northern and Jubilee lines, but with the new system not expected to be up and running on the Northern Line until 2011 at the earliest, Mr Jones admitted the line is likely to remain a liability for the foreseeable future.
Mr Jones said: "The new signalling will make it inherently more reliable, it really will.
"It's the single biggest thing in terms of reliability on the Northern Line. New signalling should virtually eliminate suspensions on the line owing to signal failure."
There were 20 such failures in May and another 21 in June.
In addition to making the line more reliable, it is hoped the new signalling system will result in a faster and more frequent service. Tube Lines says it will improve the line by about 20 per cent.
But Mr Jones denies that it means the next five years will cause misery for passengers.
"It won't be a case of grin and bear it' because we are doing a lot of work to upgrade it," he said. "We've got to live with the existing system for the next five years but we are making the best we can of it. We won't stop investing in the existing one just because there's a new one coming along."
Money is also being ploughed into track renewal - the reason why the line has been closed between East Finchley and Camden Town on weekends.
The bad news is that the renewal has only been in one direction.
Assuming London Underground gives its consent, Tube Lines will need to set aside another 12 or 13 weeks to do similar work in the other direction.
It is Tube Lines' opinion that weekend closures, inconvenient as they are, are better than the alternative - closing the line completely for weeks at a time.