Sadly I’m running out of time, and thank you again for your detailed reply, but a couple of points: the Clarkson example could be better handled through taxation on his earnings during his lifetime, your prices are primarily relevant to land rather than complete farms - typically in Devon/Cornwall you’d be looking at 15-30k per acre when farmhouse etc. is included, and finally the money made running a farm often ends up reinvested or used in the subsequent running of the farm, so stripping £40k out of it in your example would significantly affect the running of the farm the next year and so on. Ok, got to rush…
Did you read the article before posting this? It doesn’t concern inheritance tax and they are managing the farm, hoping to become full tenants - i.e. don’t and won’t own the farm.