A Newport Crown Court trial is continuing of a police officer accused of lying to avoid a speeding ticket.
Sergeant Williams was caught by a mobile camera near junction 35 of the M4
Sergeant Alun Williams, 38, was caught doing 102mph on a speed camera on the M4 as he headed towards Bridgend.
The jury heard how three other officers in the car had no idea they were meant to be chasing a criminal, as claimed by Sergeant Williams.
The advanced police driver, from Tonypandy, Rhondda, denies perverting the course of justice.
The prosecution claims that Sergeant Williams made up a story that he was on an official police pursuit, chasing a banned driver along the motorway.
He told police he was chasing a white Volvo sports car but a jury heard no car of that sort was on the motorway CCTV cameras at the time.
Three other officers were in the car at the time, on their way back to police headquarters in Bridgend, but told the court they knew nothing about the disqualified driver.
Pc Richard Chilcott said: "I had no knowledge of any pursuit, chase or follow of any vehicle on that day."
The court heard on Thursday that Pc Chilcott was a rear passenger in the Toyota Previa and had noticed Williams braking near the speed camera.
"While we were on the M4 there was a sudden decrease in speed of the vehicle," he said.
"My first impression was that it was traffic congestion or a hold-up. But I remember looking up and seeing a speed van on the bridge overhead."
Pc Dean Marshall was another passenger in the hire car, which was travelling back from the Wolves v Sheffield United play-off match at the Millennium Stadium in Cardiff.
Pc Marshall said: "There was nothing said in the car nor any action taken to make me believe that at any time of the journey that Sergeant Williams was following or pursuing another vehicle."
The jury was shown a video of Mr Williams allegedly driving at 102mph an hour.
Pc Brian Davies, who was operating the speed gun that caught Williams, said he knew the sergeant and had worked with him in the past.
"As a police officer he is very pro-active and I have never had cause to doubt his integrity," he said.
Prosecutor Matthew Roberts said: "He simply fabricated the story to escape prosecution.
"Williams said he was pursuing a disqualified driver. But this was a blatant lie."
An investigation was started after Sergeant Williams allegedly confessed making up the story to a colleague in the police canteen.
He denies perverting the course of justice by submitting a false police notebook entry and applying for exemption from prosecution.
The trial continues.