Bertha May Walker (1912-1975), labour activist, was born on 8 July 1912 at Richmond, Melbourne, elder child of Victorian-born parents Thomas Percival Laidler, bookseller's assistant and socialist, and his wife Christiane Alicia, née Gross. For most of Bertha's childhood the family lived above Will Andrade's bookshop in Bourke Street. Known as 'Bubbles', she retained memories of meetings on the Yarra Bank and in the rooms of the Industrial Workers of the World. Her teddy bear was ripped apart by police during a raid on the Laidlers' living quarters. She went to Queensberry Street State School, Carlton, which she called 'a school of poor children'. At the age of 8 she attended her first lectures on communism and meetings of the Socialist Sunday School. On 5 May 1924 she headed the eight-hour-day procession as the May queen.
After leaving Stott's Business College, Laidler entered the Victorian Public Service and worked in the motor registration branch. She attended classes run by the Communist Party of Australia and took charge of the Young Comrades Club. In 1928 she began what was to be an intermittent relationship with the communist writer Judah Waten; they sailed for Europe in March 1931. Settling in London, they found jobs with the National Unemployed Workers' Movement. She joined the Communist Party of Great Britain and was on the N.U.W.M.'s national women's committee. Returning to Melbourne in May 1933, Laidler was active in the CPA, the Shop Assistants' Union of Victoria and the Spanish Relief Committee, as well as being one of the few women associated with the Swanston Family Hotel group of left-wing artists and intellectuals.
Laidler worked for the Federated Ironworkers Association of Australia in Melbourne, Sydney and Newcastle, before following Waten and Noel Counihan to New Zealand in 1939. She was employed in the office of the Motor Transport Workers' Union in Wellington and for six months edited the illegal newspaper of the Communist Party of New Zealand. Back in Melbourne from late 1940, she was a member of the CPA's State committee during the period in which the party was proscribed, and soon became a full-time worker for the party and chairman of its eastern district, based at Richmond. In June 1943 she stood as CPA candidate for the Legislative Assembly seat of Richmond, winning 32 per cent of votes.
From 7 May 1945 to 15 May 1946 Laidler served in Melbourne with the Women's Auxiliary Australian Air Force. She moved to Darwin in October as a bookkeeper-typist and journalist with the North Australian Workers' Union. There, on 17 December 1946 at Melville Church, she married with Presbyterian forms Joseph Walker, the union's secretary; they moved to Melbourne next year. Busy starting a family and earning a living as a shorthand-typist, she stopped most of her political involvement, although her views remained close to those of the party.
In 1956 Bertha Walker began collaborating with her father on his reminiscences. A founder (1962) of the Melbourne branch of the Australian Society for the Study of Labour History, she became a regular contributor to its newsletter, Recorder. In 1966 she formed the Anti-Conscription Jubilee Committee to honour veterans of the 1916-17 campaigns. Conscious of the relevance of history to current struggles, she published a pamphlet, How to Defeat Conscription(1968), which sold nearly two thousand copies.
Walker's book on her father's life and times, Solidarity Forever, appeared in 1972. Many of its vivid descriptions of incidents, including the 1923 police strike and the protests in 1924 against the execution of Angus Murray, were drawn from her own memory. Part memoir and part history, the work is an invaluable resource; its thoroughness, good humour, commitment and lack of pretension reflected her personality. She returned to a manuscript she had begun earlier, dealing with the Depression; it combined her own research with accounts by participants in the events, but was not published. Predeceased by her husband and survived by her son, she died of liver disease on 24 May 1975 at Carlton and, after a secular service conducted by John Arrowsmith, was cremated.