The suspect being sought over the stabbing of a man on a train in Surrey has been arrested along with another person, British Transport Police said.

Officers attended an address in the Farnham area at around 6am on Saturday where the man, whose age is yet to be confirmed, was detained on suspicion of murder.

A 27-year-old woman was also arrested on suspicion of assisting an offender, police said.

It was confirmed on Friday evening that the 51-year-old victim of the incident had been travelling onboard the South Western Trains service with his 14-year-old son.

Police said on Saturday that investigators were now confident the incident “was not a random assault”. 

They added that the victim and the suspect had been involved in an altercation lasting just three minutes after boarding the train, before the victim suffered multiple stab wounds in an episode of “extraordinary violence”.

Assistant Chief Constable Sean O’Callaghan told BBC Breakfast that enquiries had found that the two men were involved in a “verbal discussion” which lasted “from three to four minutes” from one carriage to another.

“That argument escalated to the unprovoked violent attack that sadly resulted in the death,” O’Callaghan said.

Detectives had earlier said the two men were not thought to have known each other, and it is unclear at this stage as to whether this has changed beyond confirmation of the three-minute altercation. 

“This is, as far as we can see at this moment in time, an incident that has occurred when two men have been talking to one another, opposed to a random attack on a train,” O’Callaghan explained.

O’Callaghan said officers were providing specialist support to the son of the victim.

He said the man’s son was “present at the start of the argument”, adding: “He was certainly present throughout the aftermath.”

“A young boy has been present when his father has lost his life and we are doing all that we can to support where we can,” O’Callaghan added.

The incident began just after 1pm on Friday as the London Waterloo-bound service passed through the leafy Surrey commuter belt.

Both the suspect and victim boarded the train at London Road station east of Guildford, with the altercation taking place almost immediately after.

The suspect fled the train at the next stop, Clandon, and was seen by witnesses running through the small village.

Desperate attempts to save the victim were made when the train stopped at the following station, Horsley, before he was pronounced dead at the scene.