I think he means this:

http://www.lovepotatoes.co.uk/king-edward/
http://en.wikipedia.org/wiki/King_Edward_potato

The Wikipedia page says they were introduced in 1902 and named after King Edward I&VII.

I was once part of a group of musicians in a play about potato pickers in Midlothian. We formed a band afterwards. One name we considered using was "King Edward and the Pentland Squires".