Signal failures have caused major delays and disruptions on trains between Sussex and London today.
Lights were stuck on red across large parts of the network, including the Brighton Mainline, for almost an hour after problems developed at about 10am.
Frustrated passengers were left stuck at stations or on trains while the fault was fixed.
Prosective Parliamentary Candidate for Brighton Kemptown, Nancy Platts, ended up missing a funeral because of the delays.
She tweeted: "About to miss a funeral because your trains from Brighton to London appear to be going nowhere."
The problem has now been fixed but people are being warned to expect delays of up to 40 minutes as the service gets back to normal.
A spokesman for Southern Railway said people were likely to experience knock-on effects of the delays for a while but any disruption should be resolved before the start of this afternoon's rush hour.