Hi Max,
Try the Gloucestershire board instead. I'll bet someone there can help you with this.
I've got ancestors from Bristol, too.

The other side of the family (from London) has people disappearing for many years and no trace at all of several others - even though I know that they were very much alive!
I'm sure you'll get a good response on the Gloucestershire board. Ask about the British Isles Vital Records Index (BIVRI). Someone could perhaps do a lookup of George Knight to find out when he died and perhaps where he's buried. Maybe someone with a relative who was in the police force can advise you how to contact their archives.
I found a relative who was in the police force in London here:
http://www.lightage.demon.co.uk/POLNOTES.htm I couldn't find your George Knight listed, but you might want to double-check just in case.
I'm quite new to all this myself, but I hope that's of some use to you.
Good luck and best wishes,
Vicky