Odd question I know, but I'm going on this route tomorrow (to see the
Kelvedon Nuclear Bunker, as per an earlier query).

I had a serious ear operation last week and underground tube journeys or
sudden changes in pressure due to trains entering a tunnel can be dangerous
for the next couple of weeks.

Obviously, going into a tunnel by foot is fine. ;-)

I assume that the train to Brentwood, that stops at more stations, goes
slower than the Shenfield one. But even so, I wouldn't want to risk sudden
tunnels.

Thanks in advance!