Thanks for this, I found the link to the page on binary searching sorted text files before I posted this, though failed to see the comment mentioning File::SortedSeek!

You're right, it does exactly what I need and I've now managed to get it working with the log file as expected, so thank you!

I've found I will probably run this script every 5-10 minutes in order to reduce the amount of RAM required to run this as it does get quite hungry.