I (Mark Brader) asked Charles Pottins:
So was this monochrome map like the early 1950s full-color maps?

He replied by emailing me a scan of it. Thanks!

First, it's not only monochrome, but it doesn't distinguish the
various Underground lines at all. They are all drawn as a simple
black line, and there is no legend except for a tiny one just showing
the interchange symbol. (In places where the regular diagram of that
time illogically showed two separated colored lines for lines sharing
track, such as the Uxbridge branch, this one shows two separated
black lines.) Only the Waterloo & City, then the one non-Underground
line shown on Underground maps, is distinguished, as a hollow line.

This is quite different from the monochrome diagram in *my* A-Z, from
about 1970, which shows the Northern solid, the Circle hollow, the
District as a line of dots, the Metropolitan as a line of squares,
and uses harder-to-describe shapes similarly for the other lines.

Next, the general layout of Charles's map is indeed of the period
I asked about. Looking at "Mr Beck's Underground Map", I see that
the diagram was redrafted in 1946 and again in 1954; the general
layout of Charles's map is the one that applied in between those
dates. Also, up to 1949 the diagram showed dashed or dotted lines
for both the Central Line extension to Ongar (opened that year) and
the Northern Line extensions to Alexandra Palace and Bushey Heath
(never completed).

The next map in the book after 1949 is from 1952, and is described
as virtually identical to the 1951 version. It shows the Central
Line as open to Ongar and drops the Northern Line plans. Same with
Charles's map. This 1952 is also extremely similar in layout to
Charles's, the most similar of all the ones in the book -- but not
identical.

Specifically, the treatment of the Richmond branch and the Thames
is different from any map in the book. In the early days of Beck's
diagram the branch was drawn extending southwest while the river
ran first northeast and parallel to it, then southeast to cross it
at right angles. In 1941 when Beck began eliminating diagonals, he
drew the branch as running straight south and the river straight
east, so that Richmond was separated from the river. Some versions
in 1946-47 substituted a diagonal section between Turnham Green
and the river, but were otherwise the same, so Richmond was still
separated. Then in the 1951 and 1952 versions, the branch returned
to its original diagonal, and the river was now drawn running northeast
and then east, so the branch crossed it on a diagonal. In 1954 the
diagonals were removed, the branch again running southward and the
river now running north parallel to it, then east to cross at right
angles. Finally, after Beck was replaced by Hutchison in 1960, the
layout of 1951-52 was restored to this area, and I believe it has
remained so ever since.


But Charles's map is different again. It shows the river running
northeast and then east, as on the 1951-52 maps, but the branch goes
straight south, as on some of the other maps!

/ | / / | |
/ | / / | |
/\/ ----|---- ----|---- .-/---- .-|---- .-|----
/ /\ | | / / | | / |
/ * \ * * / * | * / *
1933 1941 1946 1951/modern 1954 Charles's

Also, Charles's map does *not* show two separated lines for the
District/Metropolitan section from Aldgate East to Barking, as I
implied above that it would, but only one line. There are also some
slight differences in the shape of things from the 1952 map, notably
the Mill Hill East branch, which is drawn longer and comes off the
main line more sharply.

So we still don't have an exact date for the thing, but it seems
to have been taken from an early 1950s color diagram, and probably
redrafted for the A-Z.
--
Mark Brader | "In a case like this, where the idiom is old and its wiring
Toronto | probably a mess, we tamper with nothing. There is always
| the danger it will blow up in your face." -- Matthew Hart

My text in this article is in the public domain.