So, after the blog was hacked and the hosting company could not restore it from a back-up, I have embarked on setting up the blog from scratch.
I needed a syntax highlighter and went in search using the WordPress dashboard. I came up with the Crayon plug-in. It certainly seems to have a far fuller feature set than the previous plug-in I used.
UPDATE: This Plugin appears to no longer work: https://wordpress.org/support/plugin/crayon-syntax-highlighter/
I have switched to Enlighter – Customizable Syntax Highlighter