2015 Looks like a good year to do the Thames Path NT.

[Diamond Backpacker]

Passing Runnymede in the year of the 800th Magna Carta anniversary would be great.
 
The Thames Path is not the best NT for sure and in the cowparsley season a backpacker needs stilts to see the river but the LDWA registers do encourage walkers to experience a wide variety of UK locations. When its not on its 3 day holiday to London the Salisbury Cathedral copy of Magna Carta is displayed very well there.
 
http://www.dailymail.co.uk/sciencetech/article-2361985/Medieval-reunion-Four-surviving-copies-Magna-Carta-brought-time-celebrate-800th-anniversary.html