John Rowland, writing from memory...
Many or most deep tube stations have a 1 in 30 fall on leaving the station,
to aid acceleration. Some of the earlier stations have a 1 in 30 climb
before the station to aid deceleration, but the newer stations have a 1 in
60 climb ...

I've just looked through "Rails Through the Clay" and Lascelles's book
on the City & South London Railway, and I find no mention of the climb
to assist deceleration being 1 in 30 anywhere. On the C&SLR neither
book mentions a number, on the rest of the early lines only 1 in 60
is mentioned, and on the newest lines it's 1 in 50.

There is no gradient in passenger use steeper than 1 in 30.

That seems to be true. And the steepest *climbing* gradient I found
mentioned was 1 in 40 near the Camden Town junction.

These sources do not cover the subsurface lins, though.

Of course, the all-time record for lines now part of the Underground would
be the original C&SLR route near King William Street station, which was
used only from 1890 to 1900. Since they were going to use gradients
since they were going to use cable haulage, not electric locomotives,
they built the station shallow and hence required steep gradients.
Uphill the steepest in the area was 1 in 40, but downhill it was 1 in 14.)
--
Mark Brader, Toronto | "If you wish so, we write your consummations
| on your bill." --Swiss hotel services handbook

My text in this article is in the public domain.