The Truth About This Island Cornwall

I remember, as a boy, camping on one of the moors with the scouts and the scoutmaster saying, as he nonchalantly brushed off cuckoo-spit from his pantaloons, "There are only four miles of land that separate Cornwall from England." I always believed that what the scoutmaster said was the truth.... and last night in the pub this point reemerged...

Is it true?
If it is true what does it mean?
If its not true why would he lie to me?


This morning I decided to mount an expedition to the source of the River Tamar to see if it was true.

• Hiking Books: Check.
• Waterproof coat: Check
• Compas: Check
• Shirt: Check/ Plaid
• Kendal Mint Cake: Check
• Google Earth: Check.

And what I found was that... yes... the river Tamar goes up to a point 4.3 miles from the north coast, as you can see in this expedition map I have painstakingly prepared:

Explore in Google Maps

Only four miles of land. The scoutmaster was right about this fact. Other facts he mentioned such as the need for "one on one woggle polishisng" I am still finding a tad on the moot side.