Commuters heading to London faced delays when a driver boarded the wrong train and was forced to turn back.
Rail operator First Great Western has apologised for the blunder which saw a train heading for London Paddington confused with one set for Swansea in Wales.
A spokesman for the rail company said a driver and crew had mistakenly boarded the Wales-bound service out of Banbury in Oxfordshire.
Realising their error, the crew decided turning back was the "simplest thing to do", FGW said.
But the error on Monday evening caused delays and left passengers confused as other trains cleared the line so the wayward train staff could get back on the right track.
<blockquote class="twitter-tweet" lang="en">Train driver on <a rel="nofollow" target="_blank" href="https://twitter.com/FGW" class="body-link" data-vars-item-name="BL-69811-https://twitter.com/FGW" data-vars-event-id="c23">@FGW</a> apologises for 32-minute delay. "This is due to a driver boarding the wrong train and taking it on the wrong route"— Callum May (@callummay) <a rel="nofollow" target="_blank" href="https://twitter.com/callummay/status/585160331535712256" class="body-link" data-vars-item-name="BL-69811-https://twitter.com/callummay/status/585160331535712256" data-vars-event-id="c23">April 6, 2015</a>
<blockquote class="twitter-tweet" lang="en">Stuck on delayed train because a driver ahead has taken the wrong train on the wrong route!— Master Keys (@masterkeys) <a rel="nofollow" target="_blank" href="https://twitter.com/masterkeys/status/585160932554366976" class="body-link" data-vars-item-name="BL-69811-https://twitter.com/masterkeys/status/585160932554366976" data-vars-event-id="c23">April 6, 2015</a>
<blockquote class="twitter-tweet" lang="en">Trains congested due to a train going in the wrong direction, then needing to go back to get its crew? Our driver sounds as confused as us.— A. Dally MacFarlane (@foxvertebrae) <a rel="nofollow" target="_blank" href="https://twitter.com/foxvertebrae/status/585144632046186498" class="body-link" data-vars-item-name="BL-69811-https://twitter.com/foxvertebrae/status/585144632046186498" data-vars-event-id="c23">April 6, 2015</a>
A FGW spokesman said: "We are really sorry. Unfortunately the train crew boarded the wrong train.
"Realising the mistake the simplest thing to do to prevent further delays was to return them to Banbury to take the correct train forward.
"We would ask anyone caught up in this delay to get in touch."
The spokesman added that trains from Banbury leave the platform in the same direction whether they are travelling to Swansea or London, before splitting further along the line.
