The Red Rose of Lancaster is the county flower found on the county's heraldic badge and flag. The rose was a symbol of the House of Lancaster, immortalised in the verse "In the battle for England's head/York was white, Lancaster red" (referring to the 15th-century Wars of the Roses). The traditional Lancashire flag, a red rose on a white field, was not officially registered. When an attempt was made to register it with the Flag Institute it was found that it was officially registered by Montrose in Scotland, several hundred years earlier with the Lyon Office. Lancashire's official flag is registered as a red rose on a gold field.
In what century was the traditional Lancashire Flag established?