However, in 2003, Chantal attempted to help Charles appeal against his double-murder conviction.
She filed a case before the European Court of Human Rights against the French government for refusing to provide him with any assistance in his first trial.
Charles conviction was upheld by the Patan Court of Appeals in 2005.
In 2014 he was also convicted of the murder of Laurent Carrière and received another sentence.
Charles is believed to have married twice since Chantal.
Speaking to GQ in 2014, Sobhraj spoke about his reunion with Chantal in France in 1997.
He said “She left her husband and came back to Paris when she heard that I was back.
“I was still in love with Chantal, but I was with my Chinese wife who was pregnant, so I told Chantal, ‘I can’t be with you.'”
The identity of Charles’s second wife remains unknown.
The India Times reported in 2015, Sobhraj was married to his lawyer’s daughter, Nihita Biswas but Nepalese authorities have denied the marriage took place
Speaking to the Guardian, Biswas said she did not believe her husband was a killer.
She said: “Everyone has good and bad sides. Even bad deeds with good intentions can be good deeds.”
The Serpent is streaming on the BBC iPlayer now and airs every Sunday at 9pm on BBC One