Forget the generic title – this Netflix thriller should really be called “unsung legends”. Back in 1990, a handful of UK customs employees were plucked from their humdrum jobs searching suitcases or tracking down illegally imported porn mags, and transformed into undercover agents. Their mission was to bring down an international heroin-smuggling ring that was fast becoming public enemy number one.

Written and created by seasoned TV dramatist Neil Forsyth, Legends makes it abundantly clear that the so-called “war on drugs” was at least partly politically motivated. At the time, Britain’s ailing Prime Minister Margaret Thatcher needed a convenient bogeyman to vanquish so she could keep her treacherous Cabinet at bay.

Beyond the political context, though, the extent to which Legends is strictly factual feels more nebulous. Forsyth met many of the officers his characters are based on, but he’s presumably taken liberties with their personal and professional lives to protect their identities. Certainly, there’s a boilerplate quality to the backstories here: nearly every recruit is an outsider who’s been screwed over by the class system in some way.

In episode one, we see the team being assembled by principled civil servant Blake (Douglas Hodge) and former undercover agent Don (Steve Coogan), a straight-talking northerner who explains the concept of a “legend”. Essentially, it’s an alter ego so completely convincing that even the agent starts to believe it. As the series progresses, former border force officer Guy (Tom Burke), the most compelling character here, gets fully consumed by his role as a smack-moving middleman.

While he worms his way into a drug-smuggling network rooted in London’s Turkish community, plucky Kate (Hayley Squires) and buttoned-up Bailey (Aml Ameen) try to find out who’s running the main supply chain in Liverpool. Meanwhile, seemingly privileged Erin (Jasmine Blackborow) takes on a deskbound role as an all-round fixer and code-cracker who makes their field work possible.

Unfolding over six slightly convoluted episodes, Legends lacks the light touch of Forsyth’s previous crime thriller, The Gold, which dramatised the 1983 Brink’s-Mat robbery. Perhaps because Legends tells a less well-known story, Forsyth’s dialogue works overtime to remind us of the stakes involved. Within the space of a few minutes, we’re told that the operatives are trying to “pull off the biggest result in customs history” while the smugglers are plotting the “biggest heroin importation the country has ever seen”.

Thankfully, there’s enough intrigue to keep you persevering through some protracted moments. Though Coogan never fully disappears into his role, Gerald Kyd is suitably mercurial as an enigmatic accomplice called Mylonas, and Burke makes Guy an entirely convincing mole. As he seizes his opportunity to build a more exciting life, he becomes less sensitive to the impact on his understanding wife Sophie (Charlotte Ritchie) and their young daughter.

Ultimately, it’s both a testament to Legends‘ world-building, and a reflection of its flaws, that you’re left wondering whether the real-life agents may have been even more extraordinary.

‘Legends’ is streaming now on Netflix