How old is my hedge?

My hedgerow sits among these pretty ancient Welsh fields and I really enjoy the oldness of this landscape, so thought I'd try to work out how old the path could be.
A neighbour knows her grandmother used the path to get to school in the 1870s - the derelict school building still sits in it's overgrown playground at the far end. 
On a lovely sunny evening, armed with a tape measure, I tried out a method I found on http://hedgerowmobile.com/datinghedgerows.html. I measured out four 30yd stretches and counted the number of woody plants along each. I won't bore you with the science in this post, but please do ask if you'd like to know the details.
My count averaged around 6 species per 30yds - hawthorn, Crataegus monogyna, is growing on every stretch.

Comparing the number of plants to the table on Hedgerowmobile's page my hedge could be an amazing 900 years old! But looking only at the number of species gives just a rough estimate, so it could be a great deal younger.......on to the next experiment....