From Wikipedia:

"Hinckley was known to its residents for many years as "Tin 'At" (tin hat). It is reputed that, many years ago, one of the itinerant sheep drovers bragged that he could drink a hat full of ale. The local landlord put this man to the test by getting the local blacksmith to make a tin hat, which he then filled with ale. Thereafter, the town became known as "Tin 'At". Another explanation is that the people of Hinckley used to place buckets on water pumps to keep them clean and prevent the spread of illness, the bucket obviously being the "Tin 'At". A tin hat can be seen on top of the flag pole which sits on the roof of the Coral branch at the corner of Castle Street and Market Place. There is also a pub called The Tin Hat."

For more local folklore, see the Hinckley Folklore site.