An "honest and bright" husband and father who was stabbed to death on a train in front of his 14-year-old son has been named as Lee Pomeroy.
The 51-year-old's family have paid tribute to the "devoted family man", who was killed in a violent attack on a train in Surrey on Friday, the day before his birthday.
Mr Pomeroy, a married father-of-one from Guildford, was on his way to London with his son for a day out when the tragedy happened.
Paying tribute, his family said in a statement: "Lee took his son on a trip to London hoping to spend some quality time with him, which was cut short by a horrific and pointless attack.
"Lee would have had his birthday today but did not get to see his presents. He was an honest, bright person, who loved music very much; he knew history and art and he was a bachelor of science in maths.
"He was a devoted family man and did everything for his family. He was an honourable man and would always help somebody who was in trouble.
"He was a loving husband and father, he will be deeply missed by all his family."
Mr Pomeroy was pronounced dead in the carriage at Horsley station after suffering multiple stab wounds in what police have described as a "violent killing". The attack took place on a train travelling between Guildford and London Waterloo.
How the attack unfolded
:: 12.58pm - Train leaves Guildford bound for London Waterloo
:: 1.01pm - Victim and son get on train at London Road, where suspect also joins train. Attack takes places shortly after
:: 1.06pm - Suspect gets off train at Clandon and flees. Train continues with many passengers oblivious
:: 1.11pm - Train terminates at Horsley, where emergency services attend to victim
Officers arrested a 35-year-old man at a flat in Farnham at about 6am this morning. He is being questioned on suspicion of murder.
A 27-year-old woman was arrested on suspicion of assisting an offender.
Witnesses have described how police have been guarding a flat in the street since the early hours of Saturday.
Neighbour Grant Christy said police "smashed the door down".
"Initially I just heard the banging. Sounded like someone trying to kick the door in, that's what it sounded like to start with," he said.
"Then I heard the police shouting, 'put your hands up, turn around', all that sort of thing and then it went quiet.
"They led her out first with the kid, barefoot, put her in a police wagon over there, then a few minutes later they pulled him out handcuffed."
Police have sought to reassure the public, saying they do not believe the attack was random.
British Transport Police Assistant Chief Constable Sean O'Callaghan told Sky News the men joined the train at Guildford and a discussion occurred between them on the train.
"That continued for between three and four minutes," he said. "During the course of that discussion, both men moved to a second carriage, and that is where the violence ensued to the ferocity that we are now aware of and tragically that is where the man lost his life."
DCI Sam Blackburn, also from British Transport Police, said: "The investigation is moving with good progress and we are now confident to say that this is not believed to be a random assault. In the moments leading to the violent killing, both men appeared to be involved in an altercation lasting three minutes.
"Nothing justified the extraordinary violence that followed, and we are concentrating our efforts on the ongoing investigation."
The attack happened on the 12.58pm service travelling from Guildford to Waterloo. Officers were called to Horsley station at 1.15pm.
The victim's family, including his teenage son who was nearby at the time of the attack, are being supported by police officers.
A post-mortem is scheduled for early next week.