A British aristocrat has been missing nearly a month with her newborn baby and her partner, a convicted rapist

• A British aristocrat, who has been estranged from her family for years, is missing.
• Constance Marten has been missing since giving birth without medical help in January, police said.

A British aristocrat has been missing with her newborn baby and partner — a convicted rapist from Florida — for nearly a month, according to multiple reports.

Constance Marten, 35, and her partner Mark Gordon, 48, disappeared at the beginning of January after she gave birth to a baby in the back of their car, The Telegraph reported.

The broken-down and abandoned car was found ablaze on the shoulder of a highway in Farnworth, England, on January 5, police said.

They went further south and were last spotted on January 8 in the port town of Newhaven, East Sussex. They were seen carrying bags containing a tent, pillows, and sleeping bags, police said.

British police believe the family has been using camping gear to sleep rough and say they're worried about the welfare of the newborn baby, which has "possibly been exposed to sub-zero temperatures."

"We are growing increasingly concerned not only for their welfare but for the welfare of their newborn child," said Detective Superintendent Lewis Basford, who is leading the investigation, in a press release on January 13.

"Being on the move for a week must be exhausting for new parents and a newborn baby." Since then two and a half weeks more passed without a sighting.

The couple, have been living a nomadic lifestyle since leaving their home in Eltham, south-east London, in September last year, the BBC reported.

Police are offering a £10,000 ($12,000) reward for more information that leads to finding the family.

Estranged from her family

Marten's father, Napier Marten, is an aristocratic film and music producer. He also had links to the royal family: he was once a page to Queen Elizabeth II, and his mother was Princess Margaret's playmate, The Guardian reported.

In an appeal to his daughter, Napier told the Independent earlier this month: "Darling Constance, even though we remain estranged at the moment, I stand by, as I have always done and as the family has always done, to do whatever is necessary for your safe return to us."

Marten grew up in the Dorset estate of Crichel House, which is comprised of dozens of cottages, a lake, and its own cricket club. It was used as a set for the 1996 adaptation of Jane Austen's "Emma," starring Gwenyth Paltrow.

The estate was sold in 2013 for $50.5 million, with the proceeds divided among immediate family members, including Marten, the online magazine Air Mail reported.

Marten began a relationship with a man believed to be Gordon in 2016, Air Mail reported.

A friend told the MailOnline that "the family met [Gordon] very early on when they started going out, and they came to ask for money. They looked into his past and found out that he had been in jail in the US."

"They were worried because of his record and made her aware of it. Her answer was to batten down the hatches and stay with him," the friend said. "That is when she just dropped off the face of the earth."

Gordon, who is originally from Birmingham, served a 20-year sentence in Florida for raping and assaulting a woman at the age of 14, The Guardian reported. He was deported back to the UK in 2010.