In message , at 22:25:46 on Sun, 11
Dec 2016, Neil Williams remarked:

They are also useful for people who don't know London like the back
of their hand, in bad weather, and when public transport has shut for
the night. I rarely use black cabs myself, but the last one was to
and from an evening dinner (full dress), in the Winter rain, to a
banqueting location I'd not heard of before, but turned out to be
near Horse Guards Parade.

The weather aside, for which I'm sure you can carry an umbrella, may I
present to you https://maps.google.com/ and its public transport search
facility?

My date for the night is not going to happy on the tube in a cocktail
dress and high heels (or walking ten minutes[1] in the rain even with an
umbrella).

[1] That's four minutes to one tube station and six minutes from
another. I know where the stations are.
--
Roland Perry