A sniper is on the prowl, picking people off, seemingly at random, across London. It's a hectic first day for new head of PR, Liz Garvey.

Coppers. The Sweeney. Plods. The Old Bill. London's police force - the oldest in the world - is in need of a public image revamp, and Chief Constable Richard Miller has found just the woman to do it.

Introducing Liz Garvey - an American visionary from the world of new media, parachuted in to revolutionise a PR department struggling to keep up in an age of rolling news, smart phones and a news-breaking, information-hungry public.

Also running operations at police HQ are Commissioner Miller's right-hand man Deputy Commissioner Charles Inglis, loyal Staff Officer Tom Oliver and Liz's second-in command, Finn. Out on the streets Territorial Support Group (TSG) officers Davina and Robbie are tasked with upholding the peace - though Robbie would much rather be playing with the big boys of Specialist Firearms Command (SCO19), joining the likes Officer Neil. Meanwhile they're trailed by fly-on-the-wall TV cameraman Matt Coward, desperate to capture some juicy footage at the heart of the action.