By a border

1. READ/play the text
2. CLICK the picture (and video)
3. TRY this:
Q1: Why were border castles so heavily fortified?

[Answer]

From the English point of view, the biggest threat was from Scotland – and vice versa.

Some of the biggest and strongest castles were placed near the Scottish-English border

Berwick and Carlisle are two of the most fortified and strongest castles in Britain.