Line Of Duty: Every Series Ranked From Worst To Best

5. Season One

Plot: Superintendent Ted Hastings (Adrian Dunbar), DS Steve Arnott (Martin Compston) and DC Kate Fleming (Vicky McClure) investigate DCI Tony Gates (Lennie James), a decorated officer who is suspected of being corrupt.

Upon a rewatch, the first series is the one which holds up the least well.

This is partly because it's so low-key in comparison to the rest of the show's run, with a more grounded storyline, fewer plot twists and virtually no interview scenes, but it's also because season one just isn't as refined as the others.

The five-episode length isn't long enough, the storyline about Steve Arnott testifying against his former counter-terrorism colleagues is rushed and in general, the story just doesn't hit as hard as those of the other seasons do.

Nonetheless, it is still a very good start to the show and it makes for an excellent first viewing. Season one offers a gripping and intelligent mystery story that leads to a strong finale, with some truly shocking moments along the way - the ending of episode two particularly stands out in that regard.

The single greatest thing about this season is Tony Gates. He's a brilliant and complex character, who's portrayed extremely well, and his downfall is desperately sad to watch. This allows the first season to work particularly well on a dramatic level.

Overall, this was a good start to the show, even if it doesn't come close to any of the other seasons.

Best Episode: Episode five.