Her family were involved in the fishing industry and as a teenager she worked as a steward on board ships for Thomas Wilson Sons & Co., a job usually then carried out by men.

[2][3][4] A campaign was started amongst local fishermen's wives, led by Lillian Bilocca, to improve safety standards aboard the trawlers.

[1] Key demands were for all trawlers to have a radio operator on board when they put to sea; for ships to be fully manned; for improved training and safety equipment; for better weather forecasts; and for a dedicated medical vessel to accompany the fleet.

[1][5] Denness and Bilocca together with Christine Jensen and Yvonne Blenkinsop formed the Hessle Road Women's Committee to co-ordinate the campaign.

[5][6] The women organised a "Fishermen's Charter" petition with more than 10,000 signatures of support, collected within 10 days, which was presented to the British government.