Thompson, William Marcus (1857–1907), journalist, barrister, and radical, was born 24 April 1857 in Derry city, second son among four sons and four daughters of Moses Thompson, customs official, and Elizabeth Thompson (née Smith). Educated privately, he worked as a solicitor's clerk before turning at age 16 to journalism. He contributed verses to the Derry Journal, worked on the Belfast Morning News, then joined the Standard, a conservative London daily, firstly as staff member (1877–84), writing chiefly on non-political topics, then as parliamentary reporter (1884–90). He studied law at the Middle Temple (1877–80); after his call to the bar (26 January 1880) he pursued parallel careers as journalist and advocate. Shedding the intensely Orange and anti-nationalist sympathies of his family, he developed a keen interest in social and political reform, espousing radical democratic principles. Founding member of the National Liberal Club (1882), he contributed to a small journal, the Radical (1883–90), and joined the Democratic Club in Chancery Lane (1886), where his associates included leading radicals and such socialists as John Burns and Robert Bontine Cunninghame Graham. A powerful platform speaker, he addressed numerous public meetings and demonstrations, and devoted his legal practice to the representation of trade unions and political dissenters. In March 1886 he successfully defended Burns, H. M. Hyndman, and two others at the Old Bailey on charges of sedition and conspiracy arising from a Social Democratic Federation anti-unemployment march that culminated in mob violence. He acted as unofficial legal adviser to Burns when the latter unsuccessfully conducted his own defence against a charge of unlawful assembly (January 1888). He defended in the Walsall conspiracy case (1892) and represented several trade unions in arbitration over the Grimsby fishing dispute (1901).
In 1890 Thompson mounted a prominent platform as contributor to Reynolds's Weekly Newspaper – a long-standing Sunday publication of democratic opinion with wide circulation among a largely working-class audience – writing most of the front-page leading articles as well as a regular column of opinion and observation under the pseudonym ‘Dodo’. Succeeding Edward Reynolds as the paper's editor-in-chief (1894–1907), he introduced greater coverage of trade union issues, unemployment, and urban poverty, reflecting a shift in the journal's readership base from the agrarian to the industrial working class. He advocated parliamentary reform (including extension of the suffrage and abolition of the house of lords), disestablishment of the anglican church in England and Wales, Irish home rule and land reform, and cooperative ownership and tenancies as a basis for agrarian reform in Britain. His support of the demands of organised labour included restrictions on eastern European (especially Jewish) immigration – thought to be driving down wages and generating housing shortages. He served a term (1895–8) on London county council as radical member for West Newington, but was defeated in the June 1895 parliamentary election in Tower Hamlets Limehouse division. He fervently opposed the Boer war (1899–1902) as an imperialist machination of British and international capital, covetous of South African diamonds and gold. Repelled by the upsurge of jingoist militarism and disenchanted by the vacillations of wartime liberal party policy, he was chief organiser of the National Democratic League, serving as its first president (1900–02). A broad coalition of radicals, socialists, and trade unionists (David Lloyd George was one of seven inaugural vice-presidents and Tom Mann was organising secretary), the League was an effort to formalise the anti-war leftist alliance into a lasting political force. Utilising flamboyant populist rhetoric and sloganeering, Thompson hoped the League would supplant the Liberal party as the key political vehicle for reform. Despite initial enthusiasm, especially from non-party independent socialists such as Burns, the League proved unable to reconcile the disparate ideologies of its diverse membership, and quickly waned in importance. Widely read and respected across the spectrum of progressive opinion, while supportive of socialists and trade unionists Thompson never endorsed socialism as an ideology nor specifically labour-based political organisation. Ever urging cross-class progressive unity, he remained a neo-chartist radical, concentrating upon parliamentary democratisation as the necessary engine for wider social and economic reforms.
Thompson married (1888) Mary, only daughter of Thomas Crosbie (qv), editor and afterwards proprietor of the Cork Examiner; they had one daughter. His recreations included walking and cycling. He died of bronchial pneumonia, brought on by overwork, on 28 December 1907, at his home in Tavistock Square, London. He also maintained a country residence at The Hollies, Great Missenden, Buckinghamshire. His portrait was painted by John Butler Yeats (qv).