The body of Constance Marten and Mark Gordon’s baby was found with a pile of nappies in an allotment shed, a court has heard.
The baby girl named Victoria was believed to be dead “for some time”, detectives said.
The couple appeared at Crawley Magistrates’ Court charged with manslaughter on Friday after the remains were found in the Hollingbury area of Brighton, East Sussex.
Police made the discovery on Wednesday after a massive two-day search operation involving 200 officers.
The infant is yet to be formally identified and a post-mortem examination is due to take place on Friday.
On Thursday, the Metropolitan Police said it was “too early” to provide a specific date of death, adding that the infant had been dead for “several weeks”.
Marten, 35, and Gordon, 48, who are also charged with concealing the birth of a child and perverting the course of justice, spoke only to confirm their names, dates of birth and that they were of no fixed abode during a short hearing in front of a packed courtroom.
Gordon wore a grey jumper over his head throughout the hearing. At one stage during the hearing, Marten - who comes from an aristocratic family with royal connections - blew a kiss to Gordon.
Prosecutor Jeremy King briefly outlined how the charges were brought against the pair, including that the remains were found in a plastic bag in a locked shed at an “overgrown” allotment.
Detective Superintendent Lewis Basford, from the Met Police, previously said officers had been unable to determine the baby’s gender.
The case was referred to the police watchdog by the force, and the Independent Office for Police Conduct said in a statement that it was “assessing the referral to determine what, if any, further action is required from us”.
Remanding Marten and Gordon into custody, chairwoman of the bench of magistrates, Carol Lintott, said: “You are both here today ... on charges of manslaughter, concealment of the birth of a child and perverting the course of justice.
“We are sending the case to the crown court sitting at the Old Bailey.
“We are remanding you in custody until that time.”
The aristocrat and her partner will next appear in court at the Old Bailey on 31 March.
