A third man has been arrested over the alleged enslavement of a man who investigators said lived in a shed for 40 years.
The 58-year-old was found by officers at a site near Carlisle in October, the Gangmasters and Labour Abuse Authority (GLAA) said.
A 20-year-old British national is the third person to be arrested on suspicion of modern slavery offences.
He and two other men aged 79 and 53 have been released under investigation.
A GLAA spokesman said the 58-year-old man, who is British, was living in the shed with only a chair, soiled duvet and a metered television.
He has since been receiving specialist support and is now living in sheltered accommodation, the spokesman added.
GLAA senior investigating officer Martin Plimmer said: "He has made some positive progress and is clearly in a far better place than he was when we rescued him.
"We are under no illusions though that he still faces a very long road to recovery.
"He is being given every assistance but it will be a slow process, as he is severely traumatised from the alleged exploitation we believe he has endured for all his adult life."