Marina has never wavered from her story. She believes she was born in the early 1950s at a time when Colombia was in the middle of ‘La Violencia’, a brutal civil war during which hundreds of children were kidnapped by trafficking gangs.

She remembers being in her family’s rural garden shelling peas when two men took her and drove her deep into the jungle then abandoned her.

She claims a troop of white-faced capuchins befriended her, teaching her how to forage for fruits and nuts, grooming her and even leading her to safe drinking water.

‘The bond I had with those animals was real. They accepted me into their troop and they saved my life,’ Marina says as we sit in a tent at the edge of the rainforest one night. ‘It was always my dream to come back to the jungle here in Colombia, to see my monkeys again. I love my husband, I love my family. But I have never stopped loving my monkeys.

‘They are my true family for without them I would not be here. When I think of those I love most, the faces of the monkeys come into my mind. I’ve waited 50 years for this.’

Marina’s journey ‘home’ began in the Colombian capital, Bogota. The film crew, working for the prestigious American TV channel National Geographic, arranged for Marina to have a battery of tests to see if there was any biological proof of her wild tale.

Director Toby Trackman said: ‘I wanted to approach this story in a forensic, scientific way. Marina tells this fantastic tale. Well, are there any facts to back it up?’

One of the tests involved analysing Marina’s bones. Incredibly, scientists discovered her skeleton shows signs of severe malnutrition between the ages of six and ten which led to her growth being stunted – the exact time she claims she lived with the monkeys.

Another probe, similar to a lie-detector test, hooked Marina up to a set of sensitive electrodes which monitored her brain patterns.

That test proved Marina’s subconscious brain ‘registered’ images of capuchins with the same strength of feeling as pictures of her human family members, something which would be impossible to fake.

In person, Marina is a tiny, wiry woman who stands just over five feet tall.

Her lilting Spanish accent is peppered with inflections of Bradford, where she arrived at the age of 27 while working for a Colombian family who had taken her in, made her their nanny and then travelled to England on a six-month business trip.

In Bradford she fell in love with church organist John Chapman, a retired bacteriologist, and never left, raising two daughters.

It was Vanessa who encouraged her mother to go public with her story in a book, which is about to be released in paperback.

Vanessa says: ‘I grew up thinking everyone’s mum told them tales about being raised in the jungle with monkeys.

‘It never occurred to me until I was much older that there was something odd about our family.

‘I grew up with a mother who made monkey noises and climbed trees. It seems eccentric but to me it was completely normal.

‘Mum would never have gone public but I was the one who felt there was something missing, a piece of the jigsaw I wanted to find. I wanted to come to Colombia to find my human family, Mum wanted to find her monkey family.’

There are very few verifiable facts to Marina’s story. She has no clue where she was kidnapped from or where in the jungle she was dumped. So National Geographic hired  a team of researchers who attempted to piece together clues using descriptions of the flora and fauna she described.

Primatologist Dr Thomas Defler showed Marina a series of photographs of monkey species found in the Colombian jungle. She immediately picked out the white-faced capuchins which live in the jungles along the north-east border of Colombia with  Venezuela, near Cucuta, the town Marina knows she was taken to after she was ‘rescued’ from the jungle by a pair of hunters – and sold to a brothel owner.

Dr Defler was initially sceptical about Marina’s claims but later said her story was ‘plausible’ after she told how the monkeys would shake the tree branches in anger at her and used stones as ‘tools’ to break open nuts. He says: ‘We’ve only recently discovered capuchins use tools. She talks about them on the ground. An average person wouldn’t have that insight into capuchin behaviour.’

It is too dangerous to go to the jungle around Cucuta – anti- government rebels are active in the area – so instead Dr Defler arranges for Marina to visit an area of similar jungle to the north.

We fly to the remote oil town of Barrancabermeja and are driven by bus to the mouth of the massive Magdalena River, known as the Nile of Colombia.

For two-and-a-half hours we travel upstream by boat through murky waters. As the river narrows, the jungle becomes more wild and remote. Herons gaze lazily as we float past while parrots screech at the boat in anger at being disturbed. As night falls the eerie sound of howler monkeys drifts from deep in the forest.

We finally arrive at a tiny farm where we pitch our tents alongside students from Colombia’s University de Los Andes. They man a permanent research station in the rainforest studying elusive spider monkeys, capuchins and howlers.

Primatologist Carolina Castro has studied capuchins for years and is instantly dismissive of Marina’s claims. ‘Capuchins are naturally curious creatures but there is no way they would “adopt” a child. It simply wouldn’t happen.

‘If you dropped a child into this jungle the monkeys would look, they would be curious, but they would not feed it or groom it. They would wait for it to die from dehydration or hypothermia and then they would probably eat it.’

For the next three days I follow Marina as she spends hours yomping through the jungle which we reach after a 20-minute canoe journey up-river from the farm. Immediately it is clear she is ‘at home’ while the rest of us struggle in the hostile terrain. Frequent violent downpours leave the jungle floor thick with mud.

Tree branches are covered with spikes, spiders, bugs and the occasional snake. It is dark and searingly hot. The relentless swarm of mosquitoes bite through clothing, ignoring shirts and jeans impregnated with repellent. Yet Marina seems to be in her natural habitat.  

At one point we pause in a jungle clearing. She leaps on to a fallen tree trunk and rips off palm fronds with her teeth, placing them on the ground to give us a dry place to sit.

Another morning she shimmies up a palm to get a coconut which she opens by biting the top off.

Marina later says: ‘When doctors first tried to age me they studied my teeth but said they were in bad  condition. They think I was around ten when I left the jungle, which would make me 63 today.’

Marina shows us how the capuchins taught her to use two flat rocks to break open a totumo fruit: ‘We would eat the fruit and then use the shell to scoop drinking water.’

I ask student Sebastian Ramirez, who has lived in the jungle for six months, what he thinks of Marina. ‘I didn’t believe her when I heard the story,’ he says shaking his head. ‘But now she is here I can’t call her a liar. When you see her move, she is agile in a way normal people are not.

‘I’ve never seen someone her age move like that.’