I've put the complete text of Sir Howard Vincent's Police Code on my web site. It's the 15th (1912) edition of a compact guide to law, conduct, etc. for London policeman, by the man who founded Scotland Yard's CID (Criminal Investigation Department). It was used as a reference by all of the UK's police forces, and adapted to many Commonwealth forces. It should be useful to anyone researching or writing about the UK police in this period, and much of it undoubtedly applies to British police forces well into the 1920s-30s, and probably back into the Victorian era. To make it easier to use I've adapted the index which now has several THOUSAND links to entries, and put several hundred links into the text.
I've had a lot of help correcting this, but undoubtedly some OCR and formatting errors etc. remain, if you spot anything that looks wrong please let me know.
later now added a PDF version, about 1.7mb, linked from the above page. Not as tidy as I would like, it's made from a mixture of Word and HTML files to avoid having to edit a couple of thousand links by hand, but it works.