Michael Bell wrote:
In the days when railway traffic was declining fast, and it seemed
that railways might close altogether,

Can't say I ever thought that was likely. What period did you have in
mind?

I got the impression that BR developed its London commuter market
because whatever the economics, for political reasons that network
could never be shut down. Too many votes depended on it.

Can anybody confirm this?

In what sense did BR "develop" the London commuter market? If you mean
things like the Shenfield electrification, that was largely the renewal
of worn-out infrastructure and trains by up-to-date technology. Such
investment was certainly not confined to the London commuter market.
--
Richard J.
(to e-mail me, swap uk and yon in address)