The National Equine Defence League was founded in 1909 by Francis Cox to campaign for better working conditions for pit ponies and other working horses. When the League was formed, there were more horses and ponies kept than any other domestic animals. They worked very hard pulling carts and trams, and providing much of the power behind Britain's transport network. Many were treated harshly, with poor feeding and few rest breaks. Some worked 20 hours out of 24. It’s not surprising that their working lives were short.

The League's work soon expanded into helping animals of all kinds. Over the years it incorporated other charities who were carrying out similar work. In the 1920's, the League joined forces with the Carlisle Animals' Friends, run by Mr Alfred Brisco, who had started Carlisle’s first veterinary clinic for the pets of people who were too poor to afford treatment for their animals. Mr Brisco became the League's first Director, and worked tirelessly for animals until his death in 1971.

Pit ponies suffered very badly. Most went into the mines as two or three year olds, and never saw daylight again. They worked in the heat and dust underground until they died. Eye injuries were common as ponies often hit their heads against sharp edges on pit props or spars. The League's members campaigned to persuade parliament to bring in laws to protect these hard working and vulnerable creatures. Early successes included the introduction of Inspectors who toured the mines, ensuring that the ponies received enough food, clean drinking water, proper rest breaks, and veterinary attention. Later, pit ponies were given some time grazing above ground every year, and were allowed to retire when they were too old to work and enjoy their last years in comfort. When the last pit pony in Britain retired in 1996, their working conditions had changed beyond recognition.