Roberts, a lawyer and Chartist, was born in Chelmsford, Essex, on 11th December 1806, the fifth and youngest son of Thomas Roberts (1757–1829), vicar of Chelmsford and headmaster of the local grammar school. His mother was a daughter of William Prowting, a surgeon and treasurer of St Luke’s Hospital for Lunatics. Educated at Chelmsford grammar school and at Charterhouse, he was articled to a solicitor in London and was admitted to practise in 1828. On 29th August 1828, he married Mary (d. 1837), daughter of the Revd William Moody of Bathampton House, Wiltshire, with whom he had a son and a daughter.
Roberts established a legal practice in Bath, where he became involved in local politics and was a leading figure in the Bath Working Men’s Association, founded in August 1837. His involvement in the Chartist movement led to a friendship with Henry Vincent. Known as Black Jack, Roberts became a popular speaker in the West Country. He not only defended fellow Chartists in court but also found himself indicted for seditious libel at Wiltshire assizes in March 1840 following a turbulent meeting at Devizes on 1st April 1839. Sentenced to two years’ imprisonment, he secured early release in July 1840, having in the previous year (on 24th September 1839) married Mary Hill Hopkins. They had a family of two sons and two daughters. Undeterred by imprisonment, Roberts continued his Chartist associations: he was a delegate to the 1842 convention and acted as treasurer to the Chartist Co-operative Land Company. He stood as a Chartist candidate for Blackburn in the general election of July 1847 and in 1856 arranged a speaking tour for John Frost, leader of the Newport rising, on his return from transportation.
Roberts was probably the first solicitor to concentrate on trade union work. In August 1843, he was appointed legal adviser to the Northumberland and Durham pitmen’s union, and he became popularly known as ‘the miners’ attorney-general’. His avowed policy was simple: ‘We resisted every individual act of oppression, even in cases we were sure of losing’. He challenged the ‘bond’, the oppressive terms of employment under which the miners worked. In the course of many legal battles he successfully pursued against the ‘bond’, he notably secured the release of pitmen from Thornley colliery imprisoned in 1843 for breach of contract. He attacked the ‘truck’ system (the payment of wages in kind rather than cash) in what Engels described as a ‘crusade against despotic Justices of the Peace and truck masters’. He represented the miners at the inquest into the fatal Haswell colliery explosion (September 1844), and his published account of the proceedings led to a government inquiry into mine safety. From March 1844 to July 1844. he published the Miner’s Monthly Magazine as well as contributing to the union journal, the Miner’s Journal, later renamed the Miners’ Advocate.
After a prolonged dispute in 1844, the coal owners severely weakened the miners’ union, which could no longer afford Roberts’s services. From the summer of 1845, he became legal adviser to the Lancashire Miners’ Association, and settled in Manchester, where he was a friend and neighbour of Richard Marsden Pankhurst, and later of Annie Besant. He successfully fought some notable cases involving trade unionists, including the engineers from Newton-le-Willows indicted for picketing (1846). He also acted for Karl Marx in his legal affairs. In 1854, he attacked the bill restricting Sunday trading as a hypocritical encroachment on the liberties of the poor.
From 1858, Roberts was legal adviser to the Miners’ National Association until in 1863 he was forced out by the president, Alexander Macdonald. By then his approach was becoming anachronistic. He delighted in courtroom battles, boasting afterwards that he had made the coal tyrants ‘bite the dust’, but union officials now required their attorney to use the law to settle disagreements, and not as a gladiatorial contest culminating in the employers’ public humiliation. They also resented his interference in internal union matters. He did achieve a spectacular success in 1864, when he pursued the case of Janet Jones of Blaenau, near Tredegar, who had been forced by the colliery owners to work for two years without payment to repay the debts incurred at their ‘tommy shop’ by her dead father. Roberts’s court action obtained her unpaid wages and launched a national campaign against the truck system. In June 1866, he gave evidence to a select committee on the Master and Servant Acts. In October 1867, he acted for the Fenians tried for the murder of a policeman in Manchester and was ordered to be taken into custody by the judge, Colin Blackburn, for his conduct in the court. In December 1867, he helped to secure the release of Ann Justice, who was among the six Irish charged with carrying out the Clerkenwell explosion. His last major case, in 1869, involved the miners at Monkwearmouth colliery, Sunderland, where he finally succeeded in forcing the abolition of the ‘bond’. In 1871, he published a pamphlet warning of the dangers of the government’s Trade Union Bill.
Dedicating himself to the struggles of the poor, Roberts’s strongly held religious principles led him to the conviction that appalling conditions made it impossible for many people to live decent Christian lives. He visited the Holy Land with his wife in 1862 and 1863 and lectured to Church of England societies. About 1867, they moved to Heronsgate House, the old school on what had been O’Connorsville, the first Chartist land settlement, at Chorleywood, Rickmansworth in Hertfordshire. Roberts died there on 7th September 1871 and was buried in Chorleywood churchyard. His wife survived him.
 Sources: R. Challinor A radical lawyer in Victorian England: W. P. Roberts and the struggle for workers’ rights, 1990, R. Dynes The miners of Northumberland and Durham, 1873, Miners’ Advocate, 1843–1847 and The Beehive, 23rd September 1871. Archives: Newcastle Central Library: north-east strike of 1844: Northumberland Record Office: Morpeth, Bell and Buddle collection; and. Public Record Office: state papers relating to the Chartists.
 Flint Glass Makers’ Magazine, October 1851.
 K. Marx and F. Engels Collected Works, volume 4, 1975, page 542.