The 7.29am train from Brighton to London Victoria arrived ahead of schedule on Monday morning, after its arrival time was put back by three minutes.
The Southern-operated service failed to reach London at its scheduled arrival time of 8.35am for a single one of its 240 journeys during 2014.
The train firm revealed the new arrival time last week, with Monday’s service arriving before 8.38am - but still after 8.35am.
Speaking to BBC South East Today, Southern’s commercial chief Alex Foulds said the firm were trying to put together a timetable that ‘people can rely on’, adding: “We do have days when the timetable works very well but they are far and few between because they rely on everything working perfectly and all the infrastructure working well and that does not happen every day.”
Southern confirmed that the service arrived into London Victoria at 8.37am - ‘two minutes early’.
One of the main reasons behind the train’s early arrival is thought to be no longer stopping at West Sussex’s Wivelsfield station.
Passengers on southern have endured a series of delays in recent months, with the worst coming at the end of April when a power failure near Clapham Junction - Britain’s largest interchange station - plunged the rail network into chaos.
Commuters on the 6.56am Brighton - London service, now scrapped, were stuck on the train for hours, arriving at Streatham station just before 1pm, nearly five hours behind schedule.