Bamber was active in Liverpool and nationally for the best part of fifty years, present at key moments in Merseyside labour history, in the forefront of several prominent disputes.
The Liverpool they came to, dominated as it was by casual labour and irregularity of income, was characterised by poverty, ill health, squalid housing conditions and hand-to-mouth subsistence.
During the winter of 1906–7, Mary was on the rota of women who made soup to sell at a farthing a bowl from a Clarion caravan parked by St George's Hall on Lime Street.
Bamber was often up before dawn to catch bag women - who made and mended the millions of sacks used to contain and transport the products which passed through the port - as they walked to work.
Bamber gave a great deal of time - often fruitlessly in terms of actual recruitment - to talking to these women, pressing leaflets on them and persuading them to come to meetings.
Bamber spoke at meetings with the Liverpool Independent Labour Party and Women's Social and Political Union organiser, Alice Morrissey attracting crowds.