Her bloodied and bruised appearance provoked the store’s owner to call police, eventually leading to her rescue.
The 22-year-old woman was later found with fractures to her face and strangulation marks to her neck when police pulled over the vehicle she was driving in the Queensland outback.
She told officers she had been held captive by a man she had met at a party in Cairns.
The video showed the backpacker walking into the petrol station
Police stopped the SUV after petrol station staff raised the alarm
She was in a state of shock when she came in, almost zombie like
Petrol station owner
Queensland Police said the man had damaged and invalidated her passport, possibly to stop her from escaping.
The petrol station owner said: “She was in a state of shock when she came in, almost zombie like.
“Then she walked in, wearing a black summer dress and said she couldn't pay for the fuel. Tears were running down her face.
“But what struck me were her black eyes. She looked bad.”
After explaining she could not pay for the fuel, the backpacker got back in the car and drove away.
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The victim walked into a petrol station of Queensland's Warrego Highway
Minutes later police were called and officers believe they saved her life after arresting the suspect who was hiding under clothes in the back of the vehicle, which they had been travelling around the state in since early January.
Detective Inspector Paul Hart told a press conference: "Police were really just attending a routine job in relation to a driver that was unable to pay for petrol."
But they noticed she had various injuries and was "overly alarmed" by the officers' presence when they pulled her over in Warrego Highway, Mitchell, around 300 miles from the east coast city of Brisbane.
Det Insp Hart said: ”She advised that over a period of weeks she had been held against her will by the male person located in the vehicle.
"It was established they had previously had a relationship but at some point it had soured and he basically deprived her of her liberty and committed a number of offences against her as they travelled around the state.
"What she has experienced is no doubt horrific and terrifying and we commend her for taking the opportunity to speak to our police.
Police rescued the British backpacker from her ordeal on the remote Warrego Highway
He continued: "We have potentially saved this young girl's life. Given what's happened to her, the extent of what's happened over the period of time, anything might have transpired."
She has spoken to family in the UK but is unable to return while a new passport is arranged.
The woman, who police believe had been in the country since 2015, was treated in hospital for injuries which also included scratches and cuts to her neck and bruising to her body.
The back of the SUV where police found the suspect hiding under a pile of clothes Mia Ayliffe-Chung: 21-year-old British backpacker stabbed to death in Australia Thu, August 25, 2016
Mia Ayliffe-Chung was stabbed to death at a hostel in North Queensland, Australia
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Police and backpackers outside the hostel in Home Hill, Queensland, Australia, where a female Brit backpacker was stabbed to death
The suspect, from the Manunda suburb of Cairns, appeared in court on Monday charged with a string of offences, including four counts of rape, eight counts of assault and four counts of strangulation.
He also appeared in custody at Roma Magistrates' Court accused of two counts of deprivation of liberty, two counts of wilful damage, one count of possessing dangerous drugs, one count of possessing drug utensils and one count of obstructing police.
A Foreign Office spokesman said: "We are supporting a British woman following an incident in Queensland and remain in contact with the local authorities."
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