Needed: a castle for a young, ballad-inspired nobleman in the late 12th century. A place with just enough recorded history to set its significance in that specific timeframe—while, at the same time, be not so overdrawn and exposed that its history would have to be twisted past all recognition and to the chagrin of historically-minded readers... (Yes, you know who you are... and I'm one of you.)
Tickhill Castle, also known as Blyth (or Blythe), filled the need.
After all, when you're trying to breath new life into an old warhorse of a myth—the Robin Hood legend—you can't be altogether satisfied with same ol'-same old'. Familiarity is comforting, but it can certainly breed the proverbial contempt. So, while choosing the commonly-used 12th century connection was not a difficult call for someone whose favourite movie is The Lion in Winter, there were many other options to explore. I don't really have a big killer dog in any fight about Who Robyn Actually Was, but I do have a long-held personal conviction that when"Robyn Hode in Grenwode stode", it was likely not just in Sherwood Forest but also in the Peak, in Barnsdale, in Loxley Chase. Yes, 'my' Robyn is a Yorkshireman. But not a nobleman. So why would he need a castle?