A missing aristocrat and her sex offender partner are believed to have been camping in the Sussex countryside with their newborn baby, police have said.

Constance Marten, 35 and from a wealthy family with connections to the Royal Family, has lived an isolated life with her boyfriend Mark Gordon, 48, since they met in 2016.

The couple and their child went missing early last month, with none of them receiving medical attention since then.

The Metropolitan Police has offered a £10,000 reward in the hunt for information on the trio’s whereabouts and said concerns for the wellbeing of all three “continues to grow”.

In an update earlier today, the Met said they believe the missing trio have been camping out in the countryside near Newhaven and elsewhere in Sussex.

The Argus: The couple were spotted on CCTV in Newhaven on January 8The couple were spotted on CCTV in Newhaven on January 8 (Image: Metropolitan Police/PA)

The service said it had received around 300 calls in the operation to find the pair and their baby, but “they have not led to the couple and their baby being found”.

Addressing the missing couple directly, Detective Superintendent Lewis Basford said: “Constance and Mark, your baby has spent the first month of its short life exposed to the elements when it should be safe and warm and, most importantly, seen by medics.

“After a month, you must be running low on cash. Please pick up the phone and lets us know, and at the very least, that you are ok.

“We are ready to come to you and see that you and the baby get medical attention.”

He also insisted that people should not feel concerned about coming forward with information and appealed to them to do “the right thing”.

He said: “If you have seen the family, if you gave them directions, if they got into your taxi or came into your shop to buy food, drink or nappies - no matter how small a detail it may seem - please do get in touch.

“Please also be assured that if they have paid you to provide a service, a lift, somewhere to stay or something else, you are not in any sort of trouble, we just need you to tell us what you know so that we can find them and make them safe.”

The police search for the family was sparked when officers were called to a burning car on the M61 in Bolton on January 5.

It emerged the couple abandoned the car when it broke down and took a taxi to Liverpool and on to Harwich.

Since then, the family have been spotted in east London, before moving on to north London and Newhaven, being spotted in the Sussex town on January 8.

Anyone with information can call the incident room on 020 7175 0785 or Crimestoppers anonymously on 0800 555 111.