The UK's highest court has heard complex legal argument in a landmark case said to have "huge ramifications" for the so-called gig economy.
Gary Smith, a plumber who worked for Pimlico Plumbers for nearly six years from 2005, has already won a number of court rulings that determined he could claim "worker" status even though he was described in his contract as a "self-employed operative".
Pimlico Plumbers is appealing against those decisions at a Supreme Court hearing which started on Tuesday.
Chief executive Charlie Mullins said it was different from other cases involving the status of employees, including delivery and taxi drivers, but will have "huge ramifications" on employment law for a number of industries.
Mr Smith was one of 125 contractors Pimlico Plumbers could call on to carry out jobs for its customers and had a company uniform and van which he rented.
He claimed that, after suffering a heart attack in 2011 and trying to reduce his hours, he was unfairly dismissed and a tribunal made a preliminary finding that he was a "worker" within the meaning of the 1996 Employment Rights Act.
That decision was upheld by the Employment Appeal Tribunal and again by the Court of Appeal in January last year.
The Appeal Court found Mr Smith was a worker because he was required to use the firm's van for assignments and was contractually obliged to do a minimum number of hours a week.
Lawyers for Pimlico Plumbers and Mr Mullins argued the previous rulings were wrong to conclude Mr Smith was a worker.
Thomas Linden QC told the five Supreme Court justices Mr Smith was a "skilled tradesman" and therefore in a strong position as a self-employed contractor able to command high earnings.
He added: "In this case the question is whether the provisions relating to employment apply to the claimant."
Mr Smith's legal team will argue the previous decisions were correct and should be upheld.
Lady Hale, president of the Supreme Court, and four other justices will give their ruling at a later date.