Lee Pomeroy, 51 was killed after a row aboard a train heading for London Waterloo.
Darren Pencille 36, rowed with Mr Pomeroy over aisle space aboard the train, before allegedly launching a “quick and frenzied” knife attack.
Mr Pomeroy was on his way to London with his son, 14, to celebrate his birthday.
As the pair rowed, Pencille whipped a knife out of his jacket and stabbed the dad in the neck, the Old Bailey heard.
Mr Pomeroy died a little over an hour later after suffering the fatal neck wound along with another eight to his torso and further cuts to his arm, hands and thigh in less than 30 seconds.
Jurors were shown various CCTV clips piecing together events leading up to the fatal stabbing.
Members of Mr Pomeroy’s family could not bear to watch the harrowing footage, sitting up in the public gallery overlooking the courtroom and walking out before it was played.
The IT consultant can be seen arriving at the station with his son, who stands by while his father purchases their tickets.
Pencille arrived a few minutes later and all three walk over the footbridge from platform two to the London-bound platform one.
When their train pulls up they get on through separate doors but cross paths in the aisle when they turn in towards each other.
Following a brief exchange Mr Pomeroy can be seen on the carriage’s CCTV to get up and walk after Pencille, who was wearing a zipped-up jacket, sunglasses and hat.
Jurors were played footage of the two men walking through the carriage into the adjoining one before they stop and continue arguing in a standing area close to a set of doors.
Pencille can then be seen pulling his phone out and holding it up to his ear, a call jurors were told he made to Mitchell warning: “I’m going to kill this man. He’ll be dead.“
Within 10 seconds of putting the phone away, Pencille had pulled out a knife, the Old Bailey heard.
Prosecutor Jacob Hallam QC told jurors the blade is visible on screen at 1.01.13 before a bloodied Mr Pomeroy walks back down the carriage following a scuffle at 1.01.39.
“So, we are dealing with an incident that lasts for about 25 seconds,’ he said to DC Marc Farmer, the British Transport Police officer who collected and complied the footage.
“And the jury know that in that 25 seconds Lee Pomeroy sustained 18 knife injuries.”
After the first blow had been struck, Mr Pomeroy could be seen struggling with Pencille, as blood quickly began to cover the floor around them.
Once they managed to separate one of the cameras clearly caught Mr Pomeroy’s bloodied face and torso as he walked back down the carriage and sat down.
As he did so Pencille could be seen picked up his phone, hat and glasses before jumping off the train a few moments later when it stopped at Clandon.
The court heard he was picked up soon after by Mitchell and whisked down to Chichester later that evening where she bought him a set of clippers from a Tesco Extra along with razors and food bits including fruit juice, some mac and cheese, a packet of Quavers and a Pot Noodle.
Pencille’s girlfriend Chelsea Mitchell is accused of ferrying him away from the scene, helping him change his appearance and carrying out internet searches into the killing.
The trial continues