A couple missing for 11 days with their newborn baby have a substantial amount of cash, which is helping them evade the search effort, police have said. Constance Marten, Mark Gordon and their baby have no luggage with them after most of their belongings were destroyed in a car fire, and are using cash to pay for taxis and places to stay. Detectives have also revealed that Gordon is a registered sex offender. A search was triggered for them after their car broke down and caught fire on the M61 near Farnworth, Bolton on 5 January. Police believe the baby may have been born in the car, and was less than two days old. They have since been seen in Essex, Kent and London. Marten comes from a wealthy aristocratic family. US police records have confirmed Gordon served 20 years in jail for rape and battery on a woman in her early 20s in Florida when he was 14. Police are worried for the newborn and say neither Marten nor the baby have had medical attention since the birth. The couple are understood to have lived an isolated life since meeting in 2016, with then-drama student Marten cutting off ties with family and friends. She grew up in Crichel House, a Dorset estate, as part of an eminent family who had links to the royal family. According to the Sunday Times, her grandmother was a playmate of Princess Margaret, while her father, Napier Marten, was a page to Queen Elizabeth. The newspaper reported that the family put the Dorset estate on the market in 2010 for £100m, before its sale to an American buyer. Last September, Marten and Gordon began moving around the country, staying in Airbnbs for brief periods. After abandoning their car nearly a fortnight ago, the couple then walked to the Anchor Lane bridge, where they got a taxi to Liverpool before getting another to Harwich, Essex where they were spotted on CCTV, with Marten wearing a red scarf. They were seen around Colchester on 6 and 7 January , when they took another taxi to East Ham station in east London, where they were last seen. Each time the couple are seen on CCTV, they are covering their faces or looking away, and have kept the baby covered up. Investigators say the couple appear to know how to evade the authorities – making the search for them harder. Police believe they could be anywhere in the UK and are appealing to the public to come forward with any information that may help find them. Investigators said it is unusual for hotels to accept cash payments and appealed to staff at hotels or hostels where the couple may stay to come forward. Metropolitan police Det Supt Lewis Basford said: “This is a complex investigation with officers from across the Met continuing to work around the clock to find Constance, Mark and their baby. “There is nothing to suggest that any of them have come to any sort of intentional harm – we just need to ensure they are OK, especially the baby, and do not require any medical assistance for any underlying issues. “The last confirmed sighting of them was more than a week ago in East Ham – they could now be anywhere in the UK, which is why it is vital that members of the public continue to contact us with any suspected sightings. “The assistance you’ve provided so far has been invaluable. Please don’t forget about Constance, Mark and the baby – if you see them or think you have seen them then please contact us as a matter of urgency.” Two hundred officers are working on the search and have scoured through more than 200 hours of CCTV footage since the pair were last seen on 7 January.