In 1949, a young brother and sister left a note to their parents saying they were "going away camping for a few days". It was a 700-mile, two day trip that caused panic back home and national newspaper headlines.
Thirteen-year-old Millie Richardson had an ambitious plan for whiling away the school summer holidays.
Bored of climbing trees near her home in Hitchin in Hertfordshire she plotted how to get herself to her grandmother's home at North Tolsta on the Isle of Lewis.
Millie's mother Mary was from the island and she had enjoyed family holidays there. To Millie and her siblings, their grandparents' croft with its animals and the beaches of Tolsta were "paradise".
Her brother Syd, then nine, was a willing recruit to her adventure, but their 11-year-old sister Annie refused to join them.
"She said we were crazy," says Millie, who describes her younger self as "adventurous" and a "tom boy".
Fuelled by the adventure stories she was reading at the time, Millie set about planning her journey to the Outer Hebrides.
Their provisions amounted to little more than a few pennies, their swimming costumes for the beaches at Tolsta, and some stale buns to eat on the way.
But their father, a soldier from Motherwell, later conceded the children's plan to get to Tolsta worked like "clockwork".
Waiting until both parents had left the house, the brother and sister caught a train to London and then caught the night train to Inverness - a 10-hour journey.
Millie, who now lives in Queensland, Australia, says: "I knew if we caught the right train we could connect all the way up to Inverness and then to Kyle of Lochalsh."
From Kyle of Lochalsh on the West Highland coast they planned to take a ferry to Stornoway on Lewis.
The children did not have enough money for the train, or the later ferry trip, but merged with crowds boarding the various trains.
"We were children and they just didn't expect us to have tickets," says Millie, adding that railway staff they encountered assumed they were the son and daughter of one of the adults on the train.
On the few occasions they were nearly caught, they pretended they were asleep or hid in a toilet to avoid questions.
From Inverness, the children travelled by train through the Highlands from Dingwall to Garve, Strome Ferry and finally Kyle of Lochalsh.
Syd says he felt nervous boarding the steamer to Stornoway, fearing they would be caught at any moment. But using the same tactic that had worked so well on the trains, they joined the crowd of ferry passengers and sneaked onboard.
Back home there was panic.
Millie and Syd were reported missing shortly after they started out their adventure. Annie spilled the beans that her siblings were heading for Tolsta, but the children's parents and the police expected them to be found much closer to home.
Yet, a day and a half and 700 miles later, the brother and sister were in Stornoway and steeling themselves for making the last 16 miles of their journey to granny's on foot.
Syd, a journalist who now lives in Yorkshire, says a woman who spotted them took pity on them and gave them the fare for the last bus of the day to Tolsta.
He says their grandmother was hugely relieved to see them. "She was gobsmacked. She had a big Cheshire cat smile. Everything was forgiven," recalls Syd.
A telegram was sent to the children's parents in Hitchin. As word spread of the runaways' journey, their story was reported in national newspapers.
Millie admits to having some regrets about her escapades.
"Thinking what I did to my mother and father at the time, I feel guilty about that. And so I should," she says.
Millie and Syd's story is told in a new documentary, Two Go To Tolsta, which will be broadcast on 31 December at 20:30 on BBC ALBA.