I've just Googled that Longtown Castle.Very interesting.I have long had a fascination for castles,particularly the less well known ones;such as the one near Newtown,not far from the cabin.
I really should use this interest in conjunction with riding my bike to provide a reason to get some miles in.Last year I rode over to Tutbury castle(90 minutes easy ride) & had a marvelous day out for only £4 admission,a re-enactment display,a decent cafe,a good butchers at the castle,a lecture on it's history with heavy reference to Mary Queen of Scots(another of my interests)