A French police source told AFP he "was trying to climb on to the roof of the metro when he fell. He suffered a severe head injury"
The exact circumstances of Nye Frankie Newman's death remain unclear, but the operator of the Paris underground train service said his body was found between two carriages shortly before midnight.
While friends have denied he was train-surfing at the time, a French police source told AFP he "was trying to climb on to the roof of the metro when he fell. He suffered a severe head injury."
On his Facebook page, which still features some of his sometimes illegal exploits on top of trains, high-buildings or cranes, friends have left messages of condolence and praise.
On a separate "Remembering Nye" tribute page, friend Petar Cule wrote that "he lived every moment fearlessly with a open mind and a big heart."
Globe-trotting Newman was a member of a British group that promotes parkour, a dangerous sport also known as free-running that sees risk-takers perform acrobatics or stunts while roaming around cities.
"Nye was an incredible human being who was always up for anything, he experienced things in his short life that many won't experience in their life times," said the group Brewman on its Facebook page.
The Paris metro operator RATP said Newman was part of a gang who had filmed themselves riding on top of a train travelling on an open-air stretch of track that crosses the river Seine in early December.
The RATP filed a complaint over the incident.
The day before he died, Newman posted a picture of a friend in which both of them appear to be standing precariously on top of one of the bridges of the same line high above the river.