In article , Christine
writes
One dip is on the Northern
(Bank)northbound line between Angel and Kings Cross St Pancras. I like
it because it wakes me up before my stop.

"The original City & South London Line had a signal box at a location
below Weston Rise (then called Weston Street) and the line at this point
was built on a hump like the stations. When passing the signal box,
trains experience a sudden drop as they descend from the top of the
hump."

http://www.trainweb.org/tubeprune/forum.htm#Dip

--
"It used to be that what a writer did was type a bit and then stare out of the
window a bit, type a bit, stare out of the window a bit. Networked computers
make these two activities converge, because now the thing you type on and the
window you stare out of are the same thing" - Douglas Adams 28/1/99.