A potential victim of modern slavery has been rescued after living in a shed for 40 years, according to the Gangmasters and Labour Abuse Authority.
Officers found the 58-year-old British man with just a chair and soiled bedding during a raid at a residential site north of Carlisle on Wednesday.
He was taken away to be assessed by specialist medical staff.
A 79-year-old man has been arrested on suspicion of modern slavery offences.
'Rabbit in headlights'
Martin Plimmer from the GLAA said: "The information that was given to us was that he had been kept in the shed for a period of 40 years.
"When we found him he was like a rabbit in headlights and very confused.
"He was just in the clothes he stood up in and where he was sleeping in the shed there was just a soiled duvet on the floor.
"There was no heating and it was very cold. It was conditions that no human being should live in."
Mr Plimmer said the man appeared to have been made to carry out unpaid work from the age of 16 or 17.
He said it was unclear whether the man had ever tried to leave.
"He has been traumatised for such a length of time that it will be a slow process to win back his trust," Mr Plimmer added.
He said the 79-year-old arrested man would be questioned in due course.
Mr Plimmer added: "In my long career I've never come across anyone who has been held as a slave potentially for 40 years and this, I think, could be the longest period of captivity that we have dealt with.
"It's an extremely sad and serious case."
The raid resulted from a call to a confidential helpline, Mr Plimmer said.
The operation was supported by the National Crime Agency and Cumbria Police.
Carlisle City Council's private sector housing team, which was investigating possible health and safety breaches, was also involved.