Channel 5's police drama Suspects feels like a documentary. It looks like a fly on the wall doc but the real key to its success is that there are no scripts. The actors are given a breakdown of the plot and various key pieces of information, then they are thrown together and improvise their way through each scene. It lends the finished product an air of authenticity. There's a naturalistic ebb and flow to conversations, the level of realism drawing you deeper into every story.

Suspects doesn't waste time on the investigator's personal life, resisting the urge to muddy the waters with meaningless baggage. The case always takes precedence. Each episode is also self-contained, so you can easily jump in at any point even if you've never seen it before.

The opening episode of series four concerns a missing soldier with PTSD. The team's investigations open up a messy web of damaged relationships and past sins. Suspects dispels the idea of any glamour associated with criminals or the police. The vast majority of crimes are committed by sad, desperate people. Police work is usually hard graft, sifting through evidence, desperately trying to spot inconsistencies.

DI Martha Bellamy (Fay Ripley) leads the team, tired and exasperated but driven to solve every crime. She seems to genuinely care about everyone involved from the victim to her squad. She's backed up by DS Jack Weston (Damien Molony), who favours more confrontational tactics, and DC Charlie Steele (Clare-Hope Ashitey) who has a keen eye for details and prefers the softly-softly approach. The interplay between the characters feels so believable, no one ever overplays their hand grandstanding for attention. The chemistry between the actors is utterly convincing, it's almost as if you are eavesdropping on a genuine case.

Suspects feels refreshingly different to every other cop show on TV. Low key and downbeat, the only criticism is that Suspects can be a bit depressing but that's only because it feels so real. The best original programme Channel 5 has ever produced.

Suspects series 4 premieres on Channel 5, Wed 25 Nov, 10pm.