There was a surprising number of horses and carts in and around Ashington in the late 1950s. Some were in commercial service (including a butcher called Wheatley who sold meat door to door with a horse and cart that attracted lots of flies in the summer); many were in use by sea-coalers, scavengers for coal washed out to sea and collected on the shores of Newbiggin, Lynemouth and Cresswell.
Seacoaling went on until the demise of the pits at the end of the twentieth century. Here's a short film about seacoaling around the area .
A few of the horses to be seen around town or in the nearby fields, were retired pit ponies, still employed for haulage in North East mines at the time of the story and, in the case of Ellington Colliery, for a good while afterwards. Even as late as 1984, 55 pit ponies were still in use according to the National Coal Board in Britain, and the majority of these were at work in Ellington.