An ancillary use is something that is incidental to the main use of a building/development. Essentially it is something that is of a minor, casual or subordinate nature. For example, many sandwich shops allow some customers to eat on the premises but this can considered ancillary to the main function as a shop if the majority of sales are to be consumed away from the premises. This is a matter of fact and degree and should the consumption of food on the premises eclipse the sales of food to be eaten off site then a change of use would occur.
