RAIB's first findings say a track irregularity was visible on train CCTV before the 13 August derailment. 30 were hurt. The line reopens 1 September.

A fault in the track was already visible on train camera footage before the Lewes derailment, the accident investigators have said in their first public findings. The Rail Accident Investigation Branch published an investigation update on 19 August. It says forward and rear-facing CCTV from trains that used the line earlier the same day shows “a track geometry irregularity existed on the immediate approach to the point of derailment, prior to the accident occurring”. The finding is RAIB’s own, published on its investigation page (RAIB, 19 August 2026).

The image RAIB chose to publish comes from a train that passed the spot at about 14:04. The derailment happened at about 15:54, roughly two hours later.

RAIB has not said what caused the accident, and it will be many months before it does. The update sets out what has been established so far and what the investigation will examine. It is worth reading in that spirit rather than as a verdict.

What happened, as RAIB records it

The train was 1F34, the 14:24 London Victoria to Eastbourne service, operated by Southern. It derailed at about 15:54 on Thursday 13 August 2026, around one mile north of Lewes station, on the East Coastway line between Cooksbridge and Lewes Tunnel. Lewes is about eight miles east of Brighton.

The train was formed of two four-carriage class 387 units coupled together. The rear three vehicles derailed and overturned onto the embankment. The front five stayed on the track.

Around 150 people were on board. Thirty were injured, and 20 needed hospital treatment, some with serious injuries.

Preliminary data from the on-train data recorder in the front vehicle shows the train was travelling at about 65mph as it approached the point of derailment. The maximum permitted speed there is 70mph. The driver applied the brakes as the train passed the point of derailment, and it began to slow.

Marks on the rails are consistent with the wheels of the rear vehicles having climbed over them.

The three things RAIB has already noticed

Three details in the update stand out, and none of them is a conclusion.

  • The irregularity was filmed by earlier trains. RAIB published a rear-facing CCTV still from a service that passed at about 14:04, noting the irregularity is visible next to white ballast bags. There was also evidence of previous track maintenance work in the area.
  • Passengers had felt it. Since the accident, RAIB says it has received “several reports of rough riding at the location of the derailment” from passengers on other trains.
  • It was hot, and the ground there moves. The temperature was about 27C, recorded at the nearest weather station, which RAIB names as Brighton City Airport, at the end of a sustained hot, dry spell. The embankment is clay sitting on alluvial deposits. Both are sensitive to changes in water content and can move as moisture levels change. RAIB says there is no evidence at this stage of a significant embankment slip before the accident, but there is evidence that some movement had previously taken place.

What the investigation will look at

RAIB says its investigation will seek to identify the sequence of events, and will also consider:

  • the exact mechanism by which the train derailed
  • the condition of the track, and how it was inspected and maintained
  • the condition of the embankment, including sustained hot weather, nearby structures and vegetation, and how it was inspected and maintained
  • the weather in the area on the day, and in the weeks and months before it
  • how effective the measures meant to manage the risks of running trains in hot weather were
  • the condition of the train, and how well the rear three vehicles stood up to the derailment
  • the emergency response
  • any underlying factors, including what was done about previous safety recommendations

The investigation is independent of the railway industry and of the regulator, the Office of Rail and Road. Findings and any safety recommendations will be published at the end.

Network Rail and Southern issued a joint statement the day RAIB reported. They said they were “very sorry that this happened on our railway” and would “carefully consider any recommendations arising from the investigation”. The statement was made jointly by Lucy McAuliffe, Network Rail’s Sussex route director, and John Whitehurst, chief executive of GTR, which runs Southern (Network Rail, 19 August 2026).

Timeline of the Lewes derailment from 13 August 2026, when the train derailed, through the release of the site on 15 August, RAIB leaving the site on 17 August, its first findings on 19 August and confirmation of the reopening date on 20 August, to the line reopening on 1 September 2026

The line reopens on Tuesday 1 September

The railway between Haywards Heath and Lewes reopens to passenger services on Tuesday 1 September. Network Rail and Southern confirmed the date on 20 August, and National Rail’s incident page still carried it at its last update on 26 August (Network Rail, National Rail).

Getting there has taken a fortnight of heavy engineering. Network Rail says the work involved:

  • lifting the three derailed carriages and removing the five that had not derailed, using two large Kirow rail cranes
  • stripping out the damaged track and ballast
  • rebuilding the embankment and relaying the track
  • testing the signalling and the other systems the railway depends on

Temporary foundations and platforms had to be built first so the cranes could work at all. McAuliffe said the site’s closeness to the River Ouse made reinstatement “particularly complex”.

Engineers will run a programme of testing and inspection before the line carries passengers again.

What it means for you

Brighton has been the way round for a fortnight, and that ends on Tuesday. Until then:

  • Rail replacement buses run between Haywards Heath and Lewes, calling at Plumpton and Cooksbridge.
  • There are still no direct trains between London and Eastbourne or Hastings. For Eastbourne, travel via Brighton and change. For Hastings, Southeastern from London Charing Cross is quicker.
  • The Brighton Main Line is unaffected, and so is the coastway between Brighton, Lewes, Eastbourne and Seaford.
  • Tickets are accepted on Southern and Gatwick Express between London Victoria and Brighton, on Thameslink between London Bridge and Brighton, on Southeastern between Charing Cross and Hastings, and on the Underground between London terminals.

One warning for the bank holiday weekend. National Rail says journey planners are reliable up to and including Friday 28 August, but that for Saturday 29, Sunday 30 and Monday 31 August they are “not yet showing up-to-date service information”. Services will be amended on those days and the planners updated only the day before. Check on the day rather than trusting a plan made now.

If you were delayed on the day of the derailment or since, keep your ticket and a note of the journey: both are needed to support a compensation claim.

Our roadworks and travel page tracks what else is shut across the city this week, and the trains to London page covers the normal timetable and fares.

Sources