Actually, what it says in the Inland instructions is a bit confusing. It does appear to mention somewhere that certain nationals do not need police clearance but I believe its worded confusingly.
What I do know is, as a British citizen, I had to send my UK police cert with my initial Inland application. It took 10 days to receive this from the UK (this was sent to Canada so probably a lot quicker being sent to a UK address).
To be honest, I doubt anyone would get PR without a clearance.