Cornwall is viewed as one of the rare Celtic holdouts on the Atlantic fringe, resisting assimilation more or less successfully. In fact, it was late to be recognized by the International Celtic Congress because the Cornish language had sunk to an extinct or nearly extinct status by the before the twentieth century. Still, its remote geography allowed for the preservation of many unusual cultural attributes as well as Cornish vocabulary and syntax, and so the Cornish delegation was able to argue that it should join the ranks of Ireland, Scotland, Wales, the Isle of Man, and Brittany.
From an English point of view, Cornwall is typically regarded as a distant and unusual English county. Many Cornish see things differently. Nationalists are quick to point out that Cornwall (much like the Isle Man) had its own governing body, which was not mentioned by the Act of Union, and so the Cornish are quick to argue that there is no legal basis to claim it is merely one of the English counties. It is a distinct duchy and many are pushing for acknowledgement from London of Cornwall's unique linguistic and political heritage. There is, for example, a strong Cornish revival movement, and local signs are frequently posted in both Cornish and English.
Regardless of how some might view Cornwall, all can agree that it is geographically removed from the core of England and its linguistic and its cultural roots provide an additional means to see it as having a separate cultural heritage.