A day before he goes on trial in the French capital, Belgian public broadcaster RTBF has released an interview with the alleged kingpin of the Paris terror attacks, recorded as he was fleeing France in the aftermath of the 2015 massacre.

Salah Abdeslam and 19 others are accused of planning, aiding and carrying out the 13 November suicide bomb and gun attacks on the Stade de France, bars, restaurants and the Bataclan concert hall that killed 130 people and injured 490.

RTBF said a reporter from its Hainaut bureau, Charlotte Legrand, had interviewed motorists while police were checking ID cards and searching cars at one of the many checkpoints thrown up between France and Belgium in the hours after the attacks.

“I don’t remember the make of the car, or the colour,” Legrand said. “There were three young men inside it who looked very tired; their faces looked worn. The one in the back was wrapped up in a kind of puffa jacket or duvet.”

The men were “not particularly friendly, but they answered my questions while their identity cards were being checked,” Legrand recalled. “But as soon as they got their papers back, they cut the conversation short and wound up their window.”

Asked what they thought of the checks, the three replied in quick succession: “This is the third one.” “The third check.” “Frankly, we thought it was all a bit over the top.” “But then we sort of understood the point of …” “Why.” “After, we saw why.” It is not clear who said what.

At the time, Abdeslam’s name had not been circulated to police as a possible suspect in the attacks and the men were allowed to continue on their way.

Legrand edited her 90-second piece, featuring the interview with “three young men of north African origin”, and thought no more of it until details of Abdeslam’s flight, with accomplices Mohamed Amri and Hamza Attou, began to emerge.

“When we started to see the CCTV pictures from the petrol station where Abdeslam stopped with Amri et Attou, our suspicions began to grow,” she said.

They were confirmed only after Abdeslam’s arrest, in the Molenbeek neighbourhood of Brussels on 18 March 2016, and the subsequent leak to the media of a conversation between him and two other inmates in Bruges prison.

Abdeslam told Mehdi Nemmouche, who killed four people in a 2014 attack on Brussels’ Jewish museum, and Mohamed Bakkali, an alleged member of the logistics team behind the Paris attacks, that he had spoken to a radio reporter while the car he was in was stopped, for a third time, outside Brussels.

Bakkali, along with Amri and Attou, who have both admitted collecting Abdeslam from the southern outskirts of Paris by car after he called them in the early hours of 14 November, are among the 14 suspects set to appear in France’s biggest-ever criminal trial, expected to last up to nine months in a purpose-built facility on the Ile de la Cite.

Six more are being tried in their absence: five are presumed dead in Iraq or Syria, and one is in prison in Turkey. Abdeslam, 31, a Brussels-born French citizen, is believed to be the last survivor from the cell of 10 men who carried out the Paris attacks. Most killed themselves or were killed by police.

He is alleged to have been central to the huge logistics operation that saw the jihadists return to Europe from Syria via the migrant route, and is believed to have escorted three bombers who blew themselves up at the Stade de France.

Abdeslam, whose brother also blew himself up in a Paris bar during the attacks, is suspected of perhaps planning to carry out his own suicide attack in Paris’s 18th arrondissement, but then backing out. He hid south of Paris after the attacks before calling Amri and Attou in Brussels at 5.30am.

Legrand said she was trying to “stay objective” about the discovery. “I did feel a certain malaise,” she said. “I was worried I would be accused of lacking awareness during this interview. I felt, bizarrely, a bit guilty. Then I recall the facts. At that moment, I simply didn’t have the information to recognise Abdeslam. Nor did the police.”