Published on Pastebin under an 'OpFreeAssange' banner, the data taken from three police sites - Hertfordshire and Nottinghamshire Constabularies, and police.co.uk - was fairly low-level by recent breach standards.

The most significant included email addresses, account passwords and PINs of police staff working on the Safer Neighbourhoods scheme. IP addresses were also exposed but most of the harm will be simple embarrassment.

"As a precaution these pages have been temporarily disabled whilst the circumstances as to how this information was obtained is investigated," read a statement form Hertfordshire Police.

"There is absolutely no suggestion that any personal data relating to officers or members of the public has been, or could have been compromised," it said.

The hacker's motivation appears to be simple nuisance.