Frost was born at Newport, Monmouthshire, on 25th May 1784, the son of John Frost and his wife, Sarah, landlady of the Royal Oak public house in Mill Street, Newport. His father died when John was very young and his mother remarried twice. Aged about sixteen, Frost was apprenticed to a tailor in Cardiff. In 1804, he was an assistant woollen draper in Bristol and the following year he worked in London as a merchant tailor. There he joined radical circles and sharpened his political education by reading Paine and Cobbett. On his return to Newport about 1806, he continued his business as a tailor and draper. On 24th October 1812, Frost married Mary Geach (née Morgan), widow of a timber dealer, with whom he had eight children between 1815 and 1826.
Frost published thirteen public letters on issues of Newport municipal politics during 1821–2. In 1823, he suffered six months’ imprisonment for libel, as part of a twenty-year vendetta with solicitor Thomas Prothero. Frost took an active part in the struggle for reform in Newport. He helped organise a branch of the Political Union of the Working Classes in November 1831 and his A Christmas Box for Sir Charles Morgan (1831) attacked agrarian distress and advocated a widened franchise, triennial parliaments, and vote by ballot. The following year, he savaged the Reform Act in A Letter to the Reformers. In 1835, Frost was elected a member of the town council of Newport and appointed a magistrate for the borough. In 1836, he was elected mayor, but he was defeated in 1837 owing to his opposition to church rates.
On 30th October 1838, Frost appeared in public in support of William Edward’s Newport Working Men’s Association and soon after was elected to the 1839 Chartist convention as delegate for Monmouthshire. This activity led to his removal from the commission of the peace by the home secretary, Lord John Russell, on 21st March 1839. Consequently, Frost’s popularity among the Chartists increased and he became a national leader. Throughout the spring and summer, Frost acted to damp down angry and restless local Chartist groups. However, following a wave of convictions for sedition, he appeared to shift his position. On 14th September the convention, weakened in numbers by resignation and arrests, was dissolved on the casting vote of Frost as chairman. Confusion surrounds his movements and intentions over the next six weeks but it is certain that he was present when plans were laid for a rising centred on Newport.
On 4th November, Frost led a large body of armed working men, chiefly miners, into Newport. Two other groups led by William Jones, a watch-maker from Pontypool, and Zephaniah Williams, a beershop keeper from Nant-y-glo arrived late or never came. Frost and his three thousand followers attacked the Westgate Hotel, where, under the direction of Thomas Phillips, the mayor of Newport, thirty-two soldiers of the 45th regiment and a number of special constables had been posted to guard existing Chartist prisoners. The relatively ill-armed and undisciplined Chartists were easily repulsed and suffered twenty fatalities with many injuries. Frost was captured the same evening, and was tried before Lord Chief Justice Tindal, Baron Parke, and Justice Williams at a special assize that was opened at Monmouth on 10th December 1839. He was defended by Sir Frederick Pollock and Fitzroy Kelly, but after a lengthy trial was found guilty of levying war against the queen. On 16th January 1840, Frost, Williams, and Jones were sentenced to be hanged, drawn, and quartered. Appeals against the sentences by several MPs and prominent public figures and large-scale national radical protest came to nothing. However, following legal review, it was agreed by the government on 1st February 1840 that the sentences be commuted to transportation for life to Van Diemen’s Land.
Several efforts were made, especially by Thomas Slingsby Duncombe in the House of Commons, to procure the release of Frost and his associates. In March 1854, Duncombe succeeded in obtaining a pardon, conditional on Frost’s never returning to British territory. He went to America (reaching California in May 1855), lectured on his experiences, and published A Letter to the People of the United States Showing the Effects of Aristocratic Rule (1855). After receiving a free pardon in May 1856 as a result of the general pardon granted after the successful conclusion of the Crimean War, he returned to Britain on 12th July. He was welcomed in Newport and London but never regained his status as a radical leader. On 31st August, he delivered two lectures at Padiham on the ‘Horrors of convict life’ that were later printed. The following year, he published A letter to the people of Great Britain and Ireland on transportation, showing the effects of irresponsible power on the physical and moral conditions of convicts. Although it appears that it was his intention to write a series of letters on this subject, no more were published.
Frost moved to Stapleton, near Bristol, where he lived for many years in comparative retirement, pursuing an interest in spiritualism. He died there on 29th July 1877. The march on Newport in November 1839 for which Frost is remembered has been variously interpreted as a peaceful demonstration or as part of a national conspiracy to overthrow the government. There is strong evidence of a high degree of planning, confounded by a series of last-minute changes of plan and an ultimate divergence between intentions and execution. The Newport rising was indeed part of a wider plan of insurrection and was in fact the last on the British mainland.
 D. Williams John Frost: a study in Chartism, 1939 remains the standard biography. J.E. Lloyd and R.T. Jenkins (eds.) The Dictionary of Welsh Biography Down in 1940, Cardiff, 1959 has short biographies of the leading figures in the Newport rising including John Frost and Zephaniah Williams. D. J. V. Jones The last rising: the Newport insurrection of 1839, 1985 is the best study of the rebellion. Obituaries can be found in Daily News, 31st July 1877, Daily Bristol Times and Mirror, 30th July 1877 and Daily Bristol Times and Mirror, 4th Aug 1877. Archives on Frost: Gwent RO, Newport, MSS, National Library of Wales: letters, Public Record Office: treasury solicitor’s papers (11/499) and Home Office papers, 40, 41 and British Library: correspondence with Lord John Russell, Add. MS 34245