I think you are talking about the sussex chicken

sussex county

The Sussex chicken is a dual purpose breed originating in England at the time of the Roman conquest. The Sussex can be of standard size or bantam. Their large eggs are cream to light brown, and the hen lays 240 - 260 eggs a year, with the light color types being best as layers. Rarely a Light Sussex will lay a green egg.

it is just a type of chicken

Buxted is a village in Sussex where in the 1950s a man called Anthony Fisher set up a chicken farm on the American factory farming model - the first in Britain. It was this that changed chicken from being an expensive treat to the cheapest meat availabe to UK consumers.