Two parents have been found guilty of the manslaughter of their newborn daughter, who died after they took her to live in a tent in freezing wintry conditions to evade social services.

Constance Marten and Mark Gordon, who had had their first four children taken into care, went on the run with their fifth, a baby girl named Victoria, shortly after her birth in December 2022.

Despite having access to thousands of pounds from her trust fund, Marten and Gordon insisted on living off-grid, hoping to avoid having a fifth child taken into the state’s care. Prosecutors said they spent thousands of pounds on taxis to take them almost the length of England as they sought to evade the authorities, but could not find the wherewithal to provide adequate clothing and care for their child.

It was their insistence on keeping the baby with them – even if that meant her being placed in “utterly reckless, utterly dangerous” conditions in a tent in winter – that ultimately made Victoria’s death inevitable, the prosecutor Tom Little KC told the court during their trial at the Old Bailey.

The background of social services’ involvement with the family was also important, he said, because the defendants had been warned of the dangers, including of sleeping in a tent with a young child.

Speaking after the verdicts were delivered, Det Ch Insp Joanna Yorke, who led the investigation, said the couple’s “selfish actions” had resulted in the death of a baby who should have had the rest of her life ahead of her.

“We know today’s verdict won’t bring Victoria back, but I am pleased our investigation has resulted in the couple who caused her death finally being brought to justice,” she said.

The prosecution said Victoria was likely to have died from hypothermia in cold conditions in the tent, or was smothered while co-sleeping. It was alleged that Victoria was inadequately clothed in a babygrow and that Marten had got wet as she carried her underneath her coat.

The jury heard that Marten and Gordon decided to go on the run after their car caught fire near Bolton, in Lancashire, on 5 January 2023. The discovery of a placenta and Marten’s fire-damaged passport in the burnt-out vehicle prompted concern for their welfare and that of their child.

Gordon claimed that the police and other state agencies were responsible for Victoria’s death because their pursuit subsequent to the discovery of the car had put the couple in a position where they felt forced to run. But Little said the responsibility rested with them and that Victoria would still be alive had they not chosen to go off-grid.

“That is a cold hard fact in this case,” he said. “What happens thereafter is not accidental, it all follows from their total lack of parenting skills and abilities, total lack of clothing that there was to keep the baby safe … This case is about the duty that they owed to the baby, which they plainly breached.”

Marten and Gordon “are responsible for her death, not the police, not the social services”, Little said, adding: “Ultimately, when you stand back and you consider what [Marten] says … about where the baby was sleeping, it was simply too cold, she could not maintain her temperature and death was inevitable.”

Despite repeated appeals to trace them, the couple were able to evade police for more than seven weeks, eventually being traced to the outskirts of Brighton. They initially refused to tell officers anything about Victoria’s whereabouts or her state of health. It took several more days for police to find where Marten and Gordon had discarded Victoria’s body, covered in rubbish and soil in a shopping bag left in a disused shed.

Marten told the jury she fell asleep in the tent with her daughter placed inside her zipped-up coat for warmth, days after going off-grid. When she awoke, she said, Victoria was dead. She was at a loss to explain exactly how her daughter’s death had occurred. But, describing the immediate aftermath, she told the jury: “I just knew she wasn’t alive and I felt responsible because I was holding her so my assumption was that I had fallen asleep on her.”

The prosecutors argued that their failure to report Victoria’s death was an attempt to “hide potential evidence and cause of death”.

The couple were convicted of gross negligence manslaughter. They had already been convicted at an earlier trial of child cruelty, concealing the birth of a child and perverting the course of justice. They will be sentenced on 15 September.