Johnny Moloney, a traveller, befriended Cameron Biggar after finding him homeless on the streets of London in 2004.
The 30-year-old, of St Albans, Herts, told Mr Biggar - who started sleeping rough after losing his job as a night porter in London - he would find him work and persuaded him to come and live with him in Hertfordshire.
When Mr Biggar, 43, arrived in Hertfordshire, however, he was promptly housed in a shed with no sanitation.
Moloney forced Mr Biggar to work at least 14 hours-a-day laying paving slabs from 2004 until he was arrested on Christmas Day 2014, when Mr Biggar called police.
Mr Biggar was not paid at all for the first eight years as ‘repayment’ to Moloney for taking him off the streets, but was paid around £30-a-day from then on - that’s just over £2-an-hour.
St Albans Crown Court heard on Friday how Moloney - also known as Johnny Murphy - also verbally and physically abused Mr Biggar, often slapping him in the face.
He got Mr Biggar a passport, but only let him have it on escorted trips to Ireland, Manchester, Birmingham - and even around Europe - where he was forced to lay paving slabs.
At one point, Mr Biggar managed to escape, but was quickly found by Moloney, who beat him and ordered him back to work.
Moloney was arrested in December 2014 and charged with knowingly requiring another person to perform forced labour and knowingly holding a person in slavery or servitude - charges he pleaded not guilty to.
He was, however, found guilty last week after an eight-day trial and caged for four years.
The court heard how that despite being kept in servitude and forced to perform labour from 2004, the charges against Moloney only began in 2010 when the Act of Parliament on modern day slavery came into effect.
Mr Biggar told the court he saw the ‘job offer’ in 2004 as an ‘opportunity not to be homeless any more’.
Peter Shaw. prosecuting, told the court: “Mr Biggar was a vulnerable man in a vulnerable state in 2004. He was not in a great place, physically or mentally.
“May I remind the jury of what Mr Biggar, said to the caller, when he called 999 on Christmas day 2012.
“He said to the caller ‘I want to be protected from slavery”, and “What will happen to me, will the travellers be able to find me?”
Judge Andrew Bright QC said: “Cameron Biggar is a vulnerable man who suffered from alcoholism and homelessness.
“We must make sure that a vulnerable person will be protected.”
A spokesman for Hertfordshire Police said: “The court heard how the victim, who is now aged 43, lost his job in London and was living on the streets before he was befriended by Moloney, who offered him work.
“He was then taken to Bedfordshire for a brief period before being returned to Hertfordshire and forced to live in sheds and a camper van with no sanitation.
“He was also physically and verbally abused and made to work more than 14 hours a day for little reward.
“Moloney bought him a passport but he kept strong security around it and during the summer the victim would be taken to Ireland, Europe, Manchester and Birmingham and forced to lay paving slabs.
“On one occasion he escaped but was traced by Moloney and threatened before being returned to a site in Leighton Buzzard where he was forced to work again.”
Detective Inspector Pete Frost, said: “I would like to thank the victim who has spoken about his dreadful ordeal and who has helped us to bring this prosecution. “He has shown strength and courage throughout this process. I hope the sentence passed brings some comfort to him, knowing that the man who treated him in such an appalling manner have been sentenced for what they have done.
“To think that another human being was subjected to such cruelty and suffering and in such a degrading manner is abhorrent and almost defies belief, particularly considering this has happened in the twenty first century.
“Sadly, this is the reality of modern slavery – which is unfortunately happening to others somewhere else right now.
“We all have a duty of care to watch out for and report suspicious activity which may be modern slavery so that we can help and prevent further suffering.
“I would ask anyone who has any suspicions at all that someone could be being subjected to modern slavery to call police immediately or the Modern Slavery helpline on: 0800 0121 700.”
Peter Shaw, Crown Prosecution Advocate, said: “This case highlights the fact that both the police and the Crown Prosecution Service are committed to securing justice even in the most difficult circumstances and for the most vulnerable members of society.
“The victim was a vulnerable man who had been promised paid work and a place to live in a flat.
“The work was hard physical labour, consisting of digging driveways and carrying bricks. He was completely exploited by Moloney for financial gain and was treated in an appalling way.”
Moloney’s wife Shanon Loveridge, 22, who faced the same charges as her husband, had them dropped during the trial.