I don't know, a couple of years of subsidies will clear the stamp duty, and another couple of decades and it's yours simply for doing some paperwork!
http://cap-payments.defra.gov.uk/Search.aspx
It's interesting to examine the fact that Government/EU subsidies are enhancing the value of the holding. Will it be worth as much after Brexit? It certainly couldn't be economically viable as a working farm at that price.
It's a long time since the cost of any farmland was an accurate reflection of the amount of money which could be earned by farming it (if it ever was), and agricultural subsidies are only a small part of that story.