The remains of Constance Marten’s missing baby have been found, police have confirmed.

It comes after a desperate search involving more than 200 officers since she and her boyfriend Mark Gordon were found and arrested on Monday night in Brighton.

Hundreds of police officers and search and rescue experts scoured 90 square miles of the Sussex countryside in a bid to find the baby, who had not had any medical attention since being born in or near a car in Bolton on January 5.

Metropolitan and Sussex police used helicopters, sniffer dogs, thermal imaging cameras and drones.

READ MORE: The full police statement on the discovery of the baby's remains

Marten, 35, who comes from an aristocratic family with royal connections, first went missing with boyfriend Gordon, 48, when their car was found abandoned and on fire at the edge of the M61 on January 5.

From there they travelled around the country by taxi, avoiding police by paying for everything in cash, covering their faces while on CCTV and moving locations frequently, often after dark.

They were finally arrested in Stanmer Villas on Monday, minutes after a member of the public tipped off police, but their baby was not with them.

READ MORE: Live updates on Constance Marten and Mark Gordon

READ MORE: Brighton woman claims to have seen Constance Marten's tent

The pair were arrested on suspicion of child neglect and then later of gross negligence manslaughter.