First of all we invaded Norham castle. A didn't enjoy this visit as she was worried we'd be caught! We weren't really supposed to be there: the site is closed over the winter from the end of September, plus I'd mentioned to her that English trespass laws were a lot stricter than Scottish ones. However, it's normally free to get in, and it's also fairly easy to find a way in despite the gates being closed. Towards the end of our visit other people were also wandering around the grounds so A started to feel a little better about being there. The castle is huge and must have been very imposing in its time - the thickness of the walls is especially impressive.
Then we ventured a little further to visit Etal castle. This one does involve an entry fee but as we're Historic Scotland members we can get into English Heritage without having to pay, which is nice! This castle wasn't as nearly as impressive as Norham. It does have a very good little exhibition about the battle of Flodden though which I found very informative. The village of Etal itself is quite attractive and very neat and tidy (our front garden wouldn't make the grade!).
The last stop on our trip south of the border was Heatherslaw. There is a light railway that runs between Etal and Heatherslaw, but it was too late in the day for it to be running by the time we were there.