The NPAS Twitter Map is for the National Police Air Service. This shows the most recent tweet by each police helicopter in England and Wales (the Police Scotland helicopter doesn’t have a Twitter feed). Police air-support Twitter feeds are really useful for finding out why a helicopter is keeping you awake, and they’re also a good source of aerial pictures (particularly @NPASLondon and @NPAS_Redhill).
The British Transport Police Twitter Map shows the latest tweets by all of the local police teams for that force, and some of their senior officers. I chose them as the second force to create a map for because most of their accounts specify the station that the account is based at, so its easy to post them on a map.
The London Police Twitter Map shows all the police Twitter accounts in London, including those run by the Metropolitan Police, City of London Police, British Transport Police, National Crime Agency and NPAS. There are loads of them so it might take a minute to load all the tweets.
All the maps update every five minutes and tweets from the past hour are marked with a larger icon.