Born to a Jewish family in Bethnal Green in the East End of London, Rubner undertook an apprenticeship as a cabinet maker.
He joined the National Amalgamated Furnishing Trades Association (NAFTA), and also the Communist Party of Great Britain, of which he remained a member until at least the 1960s.
By this time, NAFTA had become part of the National Union of Furniture Trade Operatives (NUFTO), and was elected to its London District Committee in 1954, and its General Executive Council four years later.
[3] In 1971, NUFTO became part of the Furniture, Timber and Allied Trades Union (FTAT), and Rubner was elected as its assistant general secretary two years later.
[2] As leader, he campaigned for improved health and safety, such as the replacement of toxic foam furniture fillings.