From the BBC site at
http://news.bbc.co.uk/1/hi/england/london/4335994.stm :

"Services on the Northern Line ... have been suspended and may remain
closed on Thursday. Union bosses called for trains to be withdrawn on
Wednesday, after one ran through a red light at Mill Hill East, and its
emergency brakes failed. [I think this means the driver was instructed
to pass a red signal with the usual precautions, but the tripcock reset
itslef without stopping the train.]

It was the fifth incident on the line, and dozens of drivers are
refusing to work on safety grounds. Commuters trying to get home on
Wednesday struggled to get onto overcrowded buses, after the gates
closed at Northern Line stations.

Last Friday almost half the line's fleet did not run as a result of
brake safety checks and an extra driver being put on each train."

I would have thought that in light of this latest incident,
double-manning would have been reinstated. But it sounds as if LU
expected its drivers to continue driving single-manned trains, and many
drivers refused. Anyone know what's really happening? At the moment,
all the LU site is saying is that the line has no trains "due to
signalling system problems".

BBC1 London news this evening showed pictures of the rope that is
supposed to be at the heart of the problem. It looked like the rope that
used to be the manual tripcock resetting device on older tube stock. Is
that still its use? Seems a bit primitive for 1995 stock.

--
Richard J.
(to e-mail me, swap uk and yon in address)