The baby of aristocrat Constance Marten and her partner Mark Gordon “had been dead for several weeks” before it was discovered, Metropolitan Police believe.
The baby’s gender is still unknown and a post-mortem examination is yet to take place, Detective Superintendent Lewis Basford said in an update on Thursday afternoon.
“Based on the enquiries we’ve carried out so far, we believe, sadly, the baby had been dead for several weeks before they were found. It’s too early for us to provide a more specific date,” he said.
The investigation team is “truly devastated” and there are still “many unanswered questions”, Mr Basford said, while adding the importance of giving them “time and space” to investigate.
Remains of the baby were found by police in a woodland in an area of Brighton near where Marten, 35, and Gordon, 48, were arrested on Wednesday.
Detectives are continuing to quiz Marten and Gordon as they work to find out how the baby died. Mr Basford said the couple will remain in police custody until late Thursday evening.
Sussex Police Chief Superintendent James Collis said there has been an “outpouring of public sorrow” following the “heartbreaking discovery”.
Mr Collis said officers have been “overwhelmed” with kind messages following the “challenging” search.
Hundreds of officers from the Metropolitan Police and Sussex Police, as well as search and rescue volunteers, had been scouring 90 square miles of land in a search of the infant.
But Mr Collis said the investigation has moved into a “new phase” and the large police presence in Sussex will be scaled back.
“I once again thank the public for their patience and support throughout this investigation,” he added.
Mr Basford said: “Because we believe the death occurred during the course of a missing person investigation, we have made a mandatory referral to the Independent Office for Police Conduct. This is standard protocol for such circumstances.”
Mr Basford on Wednesday night revealed that an infant’s remains had been found close to where Marten and Gordon were arrested.
It is hoped the post mortem examination will reveal when and how the child died.
Flowers have been left at the edge of a police cordon on the corner of Stanmer Villas and Golf Drive, near where Marten and Gordon were arrested on Monday.
The couple were arrested on suspicion of child neglect, but were re-arrested on Tuesday on suspicion of gross negligence manslaughter.
They refused to divulge information on the location or welfare of the baby, leading to the extensive search operation.
Police were on Wednesday granted a 36-hour extension to keep them in custody which runs out in the early hours of Friday.
Mr Basford said it was his “very sad duty” to announce the discovery of the baby’s body.
He added: “A crime scene is in place and work at the location is expected to continue for some time.
“This is an outcome that myself and that many officers who have been part of this search had hoped would not happen.
“I recognise the impact this news will have on many people who have been following this story closely and can assure them that we will do everything we possibly can to establish what has happened.”
Marten and Gordon are known to have used a Brighton food bank last Wednesday but did not ask for baby supplies – which were available – and they did not have the baby with them.
They also did not buy any baby supplies from a convenience store shortly before they were arrested.
A huge police search began on January 5 when their car was found on fire abandoned next to the M61 in Bolton.
Inquiries revealed Marten had given birth possibly one or two days before the incident.
The pair used taxis to first travel to Liverpool, then Harwich in Essex, and on to east London, before arriving in Sussex on January 8.
They avoided detection by making payments only in cash, hiding their faces on CCTV and often moving around at night or in the early hours of the morning.
Marten grew up at Crichel House, a Dorset estate, and her grandmother was a playmate of Princess Margaret. She was a promising drama student until she met Gordon in 2016. Since then the couple have led an isolated life cut off from family and friends.
Marten’s estranged father Napier Marten is a former page to the late Queen.
He and her mother Virginie de Selliers made public pleas through the media. Police offered a £10,000 reward for information leading to the couple being found.
