Within three hours of the derailment the site of the accident had been sealed off with a five-mile cordon. The line was expected to be closed for two weeks, with Virgin Trains saying that the line would not reopen to passenger services until 12 March 2007.

Sir Richard Branson, Virgin Group chairman, visited the site of the derailment at 11:00 the following morning to comment on the incident. During his news conference at the site he said that he regarded the driver, named as Iain Black from Dumbarton, as a hero, as he had attempted to stop the train and remained in his seat to ensure the safety of passengers. Black left hospital in late March and stated that "I've got to be in the cab to help the train and it never crossed my mind to leave."

Branson also later thanked local residents for their help at the accident site, describing how he "was very impressed to hear how those kind people rallied round, opening their hearts and opening their doors to strangers in distress". Local farmers assisted the emergency services by transporting equipment using quad bikes and four-wheel drive vehicles. Sergeant Jo Fawcett of the Cumbria Constabulary also offered thanks, saying that "There are so many people who have given up their own time to contribute in some way to dealing with the aftermath of the derailment that it would be unfair to name them for fear of missing someone out."

Branson also paid tribute to the Pendolino train, comparing it to a "tank". He also added "If the train had been old stock then the number of injuries and the mortalities would have been horrendous".

As a result of the suspicion that faulty points were the cause of the Grayrigg Derailment, Network Rail checked over 700 sets of similar points across the country as a "precautionary measure" saying later that "nothing of concern" had been found.

The operation to remove the train from the site began on the evening of 1 March 2007 with the first carriages moved from the embankment. This allowed passengers' property to be retrieved and gave investigators access to the train interior, which previously had not been possible because it would have been unsafe. The last of the carriages were removed on 4 March 2007 and the A685 road was reopened.

In 2013 the British Transport Police (BTP) posthumously awarded a Chief Constable's Commendation to a member of its staff, Jon Ratcliffe, who was at the time of the disaster media and marketing manager for BTP's North Western area. He received the commendation for his good handling of media enquires in the aftermath of the crash. Ratcliffe had died in 2008 following a sudden illness.

Lambrigg ground frame, 660 yards (600 m) south-west of the accident site, controlled two crossovers, each one comprising two sets of points allowing trains to cross from one running line to the other in emergencies or during track maintenance work. These points were used only occasionally, operated locally after a release was obtained from Carlisle power signal box.

Investigations were launched by the Rail Accident Investigation Branch and Her Majesty's Railway Inspectorate. RMT rail union leader Bob Crow said on BBC News that a points failure was responsible for the incident. Experts compared the cause to that of the Potters Bar rail crash in 2002.

On 26 February, an interim report published by the Rail Accident Investigation Branch outlined the current progress of the investigation. The report contained a single conclusion, that the immediate cause of the accident was the condition of the stretcher bar arrangement at points 2B at Lambrigg crossover, which resulted in the loss of gauge separation of the point switch blades. The stretcher bars (components that hold the moving blades of the points the correct distance apart) had been found to be disconnected or missing. Of the three bars, one was not in position, another had nuts and bolts missing, and two were fractured.

Following the RAIB interim report, Network Rail released a statement in which its chief executive, John Armitt, described how the organisation was "devastated to conclude that the condition of the set of points at Grayrigg caused this terrible accident". He apologised "to all the people affected by the failure of the infrastructure".

The RAIB report noted that the Network Rail New Measurement Train ran over the site on 21 February. This train uses lasers and other instruments to make measurements of the track geometry and other features such as overhead line height and stagger, and the track gauge, twist and cant. It is not used to inspect points, but it does make a video record of the track which can be reviewed later. Responding to the suggestion that the train's video might have been used to detect the points damage and thereby prevent the accident, a Network Rail spokesman said:

The [inspection] train runs at speeds of up to 125 mph, or 95 mph on this stretch. There would be no point somebody watching it at that speed as they wouldn't be able to pick up any faults. It has to be run in super-slow motion to spot faults. The train runs for up to 18 hours a day, seven days a week. It would probably take someone most of the month to watch one day's worth of data. It's not what it's there for. It's a backwards reference tool.

Network Rail admitted it failed to carry out a scheduled visual track inspection in the area on the Sunday before the derailment.

As part of the investigation by the British Transport Police, three Network Rail employees were arrested and bailed, one in July 2007 and two in November 2007. All three were due to answer bail in March 2008 but this was extended until the end of June pending further inquiries. On 9 February 2009, the British Transport Police confirmed that none of the three Network Rail employees arrested in connection with the derailment would be charged following advice from the Crown Prosecution Service.

Immediately after the accident, all services were suspended and the First ScotRail Sleeper train, the Caledonian Sleeper, was curtailed and passengers transferred to overnight coaches.

The line closure that followed the initial service suspension saw most Virgin services terminate at Preston or Lancaster from the south, with buses to Carlisle and all stations along the route.

Trains began running on the line again on 12 March subject to a speed restriction of 50 mph (80 km/h) at the crash site. The first train was the 05:10 Manchester to Glasgow.

On 13 January 2012, the Office of Rail Regulation announced that Network Rail was to be prosecuted under Section 3(1) of the Health and Safety at Work Act 1974 for "the company's failure to provide and implement suitable and sufficient standards, procedures, guidance, training, tools and resources for the inspection and maintenance of fixed stretcher bar points". At the first hearing at Lancaster Magistrates' Court on 28 February 2012, Network Rail indicated an intention to plead guilty to the charges. On 4 April 2012, Network Rail was fined a total of £4,118,037 including costs following the court case.

Critical commentary appeared in the media concerning the knighthood awarded to John Armitt in the 2012 New Year Honours for services to engineering and construction. Armitt had been chief executive of Network Rail at the time of the Grayrigg derailment, and the family of the victim of the accident criticised the award, which coincidentally was conferred on the same day that Network Rail was prosecuted for the accident.

After a two-week hearing on one of the issues, coroner Ian Smith announced was that he would be issuing a rule 43 report. The intention of the report is to raise concerns with authorities to prevent similar incidents occurring again.

Wikinews has related news:

• Virgin Train crashes in England

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