The activism of coalmining unions in Australia, the UK, the USA and elsewhere securing improvements in safety including better legislation in the 19th and 20th centuries, has been widely researched and acknowledged. However, a relatively neglected aspect of this history was a campaign to secure worker inspectors (check-inspectors). These began in coalmining a century before similar measures were introduced for workers more generally as part of overhauling occupational health and safety laws in the 1970s/1980s. We document this struggle for mine safety in Australia and New Zealand, and the activities of check-inspectors in the period to 1925. Notwithstanding strong opposition from coal-owners and conservative governments, check-inspectors played an important role in safeguarding coalminers and improving the regulatory oversight of coalmines. Check-inspectors not only gave coalminers a ‘voice’ in OHS, but they also provided an exemplar of the value and legitimacy of worker’s ‘knowledge activism’. This system remains. Furthermore, the struggle is relevant to understanding contemporary debates about collective worker involvement in occupational health and safety.