[1] He worked as a felt hat maker and was involved in uniting various local unions into a national federation, accomplished in 1879.
He was involved in a major strike in the industry in 1892/93, and subsequently became general secretary of the Amalgamated Society of Journeymen Felt Hatters' and Trimmers' Associations.
In this role, he avoided industrial action and focused on signing workplace agreements with employers, remaining in post until his death in 1935.
[2] Mallalieu was also politically active, and served as a Labour Party member of Denton Urban District Council for twenty years, where he promoted road widening and the creation of a public park.
[3] He was also prominent in the Industrial Alliance Organisation and the General Federation of Trade Unions, serving as its President from 1918 to 1922.