On the train company’s website David Scorey explains the scale of the derailment, which caused rush hour travel chaos both yesterday evening and this morning.
The delays were worsened by a fire at Arundel yesterday afternoon and a person being hit by a train at Battersea today.
Services are slowly returning to normal, but there are still delays on some routes.
Mr Scorey writes: “I am sorry for the severe disruption caused to your journeys yesterday evening (Wednesday) and this morning.
“Yesterday afternoon, an empty train derailed as it was leaving Brighton depot approaching the mainline towards the station. “The train moved several feet off the track causing damage to surrounding power supply cables.
“Because of the nature of the incident, it was necessary to cut the power to all routes into and out of Brighton station meaning that disruption occurred across the Southern network.
“The situation was exacerbated by two separate line-side fires and a fatality on other parts of the Southern network.
“The re-railment of the train, which we had hoped would be completed overnight, took longer than anticipated and as a result, we were unable to run trains between Preston Park and Brighton this morning.
“I am sorry for the inconvenience caused to you.”
Southern are directing people to it Delay Repay services. If someone’s journey was delayed by 30 minutes or more they can claim compensation using the scheme. Go to southernrailway.com/delayrepay or pick up a form at Southern staffed stations for more information and to claim.