A mother missing with her partner and newborn baby belongs to an aristocratic family which used to own a sprawling country estate and has close links to the royal family.
Ms Marten, her partner Mark Gordon and their child were last seen on Thursday evening after their car broke down on the M61 motorway, at which point they left the road safely and walked towards Anchor Lane bridge, near Bolton.
The new mother is thought to have since been spotted on CCTV cameras while travelling inland from Harwich Port in Essex, some 250 miles away from where their car was abandoned, and then later in Colchester, police said on Sunday.
Police are urgently searching for the family, as it is feared that Ms Marten gave birth very recently and, along with her baby, is yet to be assessed by medical professionals.
The Independent now understands that Ms Marten is directly descended from the 3rd and last Baron Allington.
Her grandparents were Toby Marten, a Lieutenant Commander in the Royal Navy, and his wife Mary Anna, who had close links to the royal family, attending the Brownies pack at Buckingham Palace alongside Princess Margaret in her youth.
A notable archaeologist, Ms Marten was awarded an OBE in 1980 and appointed High Sheriff of Dorset nine years later. She was also made a trustee of the British Museum and travelled widely in aid of her profession, making frequent trips to Iran and 30 visits to Russia.
The late couple and their family lived at the vast Crichel House – used as the backdrop for several period dramas, including Emma starring Gwyneth Paltrow – the ownership of which in the wake of the Second World War became the centre of a notorious political scandal.
In what became known as the Crichel Down affair, part of the estate was requisitioned by the government in 1938 for bombing practice by the Royal Air Force, with a purchase price of just over £12,000.
After a promise in parliament from Winston Churchill that the land would be returned to its owners after the war was broken, and the purchase price vastly inflated by the government, the couple challenged the government and a public inquiry was launched.
The Martens defeated the government, winning back their land and effectively forcing agriculture minister Sir Thomas Dugdale’s resignation over the scandal – which is still held up as a landmark case in ministerial accountability and landowners’ rights.
The late couple were survived by five daughters and one son, Napier Marten, who was a Page to Queen Elizabeth II. In 1996 he took a voyage of spiritual discovery in Australia, later returning to work as a tree surgeon near Crichel House.
In 2013 it was reported that the previously 5,000-acre estate would pass instead to his eldest son Maximillian when he turned 25 that year, after the death of Mary Anna in 2010. The estate was later bought by American billionaire Richard Chilton.
Online genealogical records state that Mr Marten had a daughter named Constance, born in 1987.
Greater Manchester Police launched the appeal to find 35-year-old Ms Marten, her partner, aged 48, and the baby on Friday.
Since then a CCTV image has been released by police, taken near Harwich Port at 9am on Sunday, in which she was wearing a large red scarf. Ms Marten is also thought to have been sighted around an hour later near Colchester.
When last seen near the M61, Mr Gordon was wearing dark clothing and the baby was swaddled.
Chief Superintendent Michaela Kerr, head of public protection at Greater Manchester Police, said last week: “As a mum, I would like to make a direct appeal to Constance: Constance, I know this is an exceptionally hard time for you and you are likely feeling scared, but I promise that our number one priority is the same as yours – to keep your beautiful newborn safe.
“As you know, it’s really important that both you and your baby are assessed by medical professionals as soon as possible, so please make contact with emergency services or make your way to your nearest hospital, wherever that may be.”
“I would also like to appeal to members of the public, not just in Bolton but across Greater Manchester and beyond,” Ch Supt Kerr added.
“If you have any information about this family’s whereabouts, please do nothing more than contact emergency services. GMP can be contacted via live chat on our website or 999. Even the most minor detail might help us keep this mum and baby safe.”
Police appealed for anyone with information to contact GMP on 999 quoting 2657 05/01/23 or via gmp.police.uk