I was at Twyford station this evening (during rush-hour, so it was fairly busy). A Henley train arrived, but instead of using Platform 5, as is normal for the Henley branch, it came into Platform 4. All the regulars who were on Platform 5 were very confused that the train they were expecting hadn't arrived, until they noticed it had arrived at a different platform. However, that train, instead of forming the return shuttle to Henley, was then taken out of service. The train forming the return to Henley then also arrived into Platform 4, which turned Platform 4 into a bidirectional platform (presumably platform 5 can't be accessed from the mainline). These train movements caused the next (at least 2) trains to be ~10 mins late.
I don't use Twyford very often, but given everyone's confusion, I'd guess this doesn't happen very often?!
I don't use Twyford very often, but given everyone's confusion, I'd guess this doesn't happen very often?!