Tom Anderson wrote:
Right, but they've got two places to do it, one on either side of the
platform, which means you can have one train pulling out as another
arrives, which you can't with a single-faced platform.

Except that unless my memory fails me, you can't actually do that at
Tower Gateway, as Royal Mint Street Junction is single-lead and not too
far off the platform ends. (So you'd get a very small improvement but
not much of one.)

On the other hand, if a train is stuck in the platform for whatever
reason, right now the next train can just pull into the other platform
-- if and when TG goes single-faced, the next train will have to wait
at RMSJ, blocking the line to Bank. That could be a bigger deal.

The layout of TG and RMSJ from memory:

|--------------------------*----*--*------------------------------------
***platform***XXXextnXXX / / \ to
Westferry
|========================= /
/---*----------------------------------
/ / RMSJ
/ /
---------------------------/ /
to Bank /
----------------------------/