I'm on a "via Victoria" (anticlockwise) circle train that started from
Edgware road on platform 2, which necessitated crossing from the other
island where the westbound Hammersmith train (albeit a Metropolitan) had
arrived at platform 4.

To achieve a cross-platform change I would have had to wait until a
District Line train reversed in platform 3 (there was none present at
the time). And then changed again if I really wanted the Circle.
--
Roland Perry