A broken-down train has caused further misery for commuters suffering disruption on one of Britain's most congested lines following the introduction of new timetables.
The Network Rail maintenance train was being used for engineering work when it failed near Gatwick Airport in the early hours of Thursday.
This contributed to half of all Thameslink services on the Brighton main line being cancelled or more than 30 minutes late as of 10.30am, according to the trains.im website.
A spokesman for Government-owned Network Rail, which is responsible for maintaining Britain's rail infrastructure, said: "We are sorry for the disruption to passengers' journeys on the Brighton main line this morning.
"An engineering train has broken down in the Gatwick area, closing two of the four tracks through the area. We have engineers on site working to move the engineering train and a specialist cleaning team who are dealing with a substantial fluid leak.
"Safety is our top priority and we are working hard to keep passengers moving, but delays are expected."
Passengers travelling on the Brighton main line are among those who have suffered hundreds of delays and cancellations since new timetables were introduced on May 20.
Transport Secretary Chris Grayling blames Network Rail for being "very late" to finalise the new timetables, as well as criticising operators GTR and Northern for inadequate planning.
GTR reliability showed signs of recovery following the introduction of an interim timetable from Monday with 230 daily services removed, which makes up 6% of trains.
On Wednesday, just 4% of trains on the amended schedule were cancelled or significantly late, compared with 13% during the first two weeks of the new timetables.
But the figure rose to 17% on Thursday morning, causing dozens of passengers to express their frustration on social media.
Caolan Mahon-Pitfield, from Brighton, wrote: "3 hours. THREE HOURS. That's how long it has taken me to get to work this morning because of @TLRailUK's utter incompetence."
Vic Polkinghorne posted: "Today's particular utter failure on Thameslink is caused by a broken down engineering train ... You couldn't make it up. 45 mins late for work."
Nick Harmer added: "Dear @TLRailUK Many thanks for making me 90 minutes late for work today. You are officially the worst train company in the history of travel."