It has been causing severe delays along the line since last month - and some turmoil for the poor people manning the Piccadilly line's Twitter account. But today, the account had some - relatively - good news to share.
I am very happy to announce... Minor delays on the whole line.— Piccadilly line (@piccadillyline) December 16, 2016
Apparently we're down to just "minor delays" along the line now. Can you sense the relief?
Passengers have been suffering severe disruption along the line, which TfL had said could continue until after Christmas.
Wet leaves and cold weather make the train tracks slippery, meaning the Piccadilly line wheels often lock when braking, damaging the wheels and the tracks. Newer trains on lines such as the Circle, Hammersmith and City and District lines have wheel slide protection; older trains on the Piccadilly line, which were built in 1973, do not.
The constant questions from angry passengers proved too much at one point for one of the people working on the Piccadilly line Twitter account last week.
Sophie , I'm trying to deal with ALL tweets on ALL lines, that's how it is here, I can't do everything at once, ok— Piccadilly line (@piccadillyline) December 6, 2016
ok, sorry if I got your tweet mixed up, I won't bother for the rest of my shift, I try so hard to help you Soph, so hard— Piccadilly line (@piccadillyline) December 6, 2016
Anyway, despite all this, the Night Tube is also set to launch on the line tonight, to make sure Sadiq Khan's pledge to have five lines running the services by the end of the year, is held.
The Rail, Maritime and Transport (RMT) union had called for postponement of the launch, due to what it said were "ongoing safety concerns".
Mick Cash, general secretary of the RMT, said: "RMT has been told the problem could take weeks to fix properly. The priority in the meantime should be to run a safe and reliable service in the daytime, when most people will be using the service."
The line needs 79 trains for full service at peak times, but TfL said it needs around 25 for the Night Tube. By Wednesday evening, it had about 66 back in service.
The mayor said earlier in the week TfL was looking at the problems on the line as "a top priority".
"Teams have been working around the clock to repair the damaged wheels that were causing the delays," Khan said. "All passengers that have been delayed have also received backdated refunds."