A Frenchman convicted of murdering his wife despite her body never being found has made a confession from prison.

Cédric Jubillar, 38, sent a letter to his lawyers admitting that he was responsible for the death of Delphine at their family home in southern France in December 2020.

He also promised to lead investigators to the place where he disposed of her remains.

Jubillar was convicted of murder last year and given 30 years in jail. Throughout the trial, he insisted that he was innocent. His appeal was due to open in two months, but this may now be postponed, his lawyers said.

In a news conference on Monday, Pierre Debuisson – who took over as lawyer from Jubillar's previous team following the trial – said: "A few weeks ago he said to me, 'I need to tell you the truth. It was me.'"

Jubillar said that he killed Delphine "after yet another marital row" and that on the evening of her death he used his car to move the body, Debuisson said.

The Jubillar mystery began at the height of Covid confinement when – at 04:00 local time (03:00 GMT) on 16 December 2020 – Jubillar contacted police to report that his wife had gone missing.

Delphine, who was 33 at the time, was a night nurse in a clinic not far from their home in Cagnac-les-Mines in the Tarn department. The couple had two children, aged six and 18 months.

Police came to understand that the Jubillars did not have a happy relationship. Cedric smoked cannabis every day and barely held down a job. Delphine was in a relationship with a man she had met online.

She and Cedric were talking about divorce.

Police and locals conducted extensive searches in the surrounding countryside – with potholers descending into some of the disused mineshafts dotted across the area.

Delphine's body was never found, but a case was gradually built against Cedric, and in mid-2021 he was placed under investigation and detained.

Malika Chmani, the lawyer representing the two children, said: "We are relieved for the children. Now he needs to tell us where the body is. I think that is what is going to happen now. I hope so."