Brennan shoots much of his footage as a fly on the wall, as though he’s eavesdropping on band members’ conversations rather than conducting formal interviews with them. This approach suits the unvarnished, boots on the ground feeling of the documentary, which complements the outlook of a bunch of ageing metal-heads who refuse to cut their hair and proudly pick up their young children from school while wearing (always black) band T-shirts.

It helps that the members of Zeus are all affable gents, each prone to moments of introspection and entirely devoted to the band as their purpose in life. This isn’t Some Kind of Monster, the infamous Metallica doc that detailed, in excruciating detail, the band’s painfully contentious therapy sessions. Zeus is a family, a vocation, for these men, and there’s no doubt their hearts are 100 percent in it, even when things are tough.

Diony, who’s proudly following in his mother’s footsteps as a singer, understandably gets most of the screen-time here, proving to be a natural and surprisingly vanity-free subject (a bus-bound freak-out is a particularly telling episode). But the rest of the band gets plenty of opportunities to tell their stories too, especially one member who credits Zeus with keeping him on the straight and narrow regarding his substance abuse issues.

The Zeus members are kind of past their prime nowadays, since all the kids are annoyingly listening to reggaeton rather than metal, but the demand for the band’s music is still keenly felt, even as they play small and technically-challenged venues across Cuba (who knew metal was so popular in Camagüey of all places?). Los Ultimos Frikis sadly reveals the lack of proper music venues for bands to play in, with Havana’s impressive Maxim Rock only built in 2007.

For those in more developed countries, it’s jarring to watch a band with 30 years experience (and more than enough pull with punters) rocking out on makeshift stages simply because they have no other choice. The change that occurs following Barack Obama’s trade agreements with Cuba, and how that moment of prosperity is over before it’s even really begun once Donald Trump is elected, again impacts on the country’s musicians and fans considerably.

Los Ultimos Frikis provides a fascinating glimpse into a world where one might have to wait 25 years to see a favorite, and even home-grown, band play, which makes Zeus’ staying power even more impressive. It is genuinely kind of amazing they’ve survived this long, given how everything in Cuba, as the members are keen to remind the audience, is linked to the government.

These men are rebels and revolutionaries just by virtue of their continued existence. It’s worth noting, too, that their music is pretty great, and much easier on the ear than normies would reasonably expect looking at them. Their lyrics, which are cleverly presented onscreen in different, more metal-head-friendly lettering than the film’s subtitles, are proudly political, standing in defiance of a brutally communist regime.

Los Ultimos Frikis is executive produced by Dave Lombardo, himself a Cuban-American and founding member of legendary metal band Slayer, who also provides additional music outside of Zeus’ own back catalogue, so its rock and roll bonafides aren’t in dispute. At its heart, though, this is a sweetly affecting story about fighting to do what you love. A happy ending isn’t even strictly necessary because Zeus’ trajectory is compelling enough as it is.

Still, with any luck, Brennan’s lively and fascinating documentary will bring more attention not just to Cuba’s continuing struggles but to Zeus as a band. They’re legends at home, but surely after 30 years, they deserve a shot at worldwide fame too.

Joey Keogh (@JoeyLDG) is a writer from Dublin, Ireland with an unhealthy appetite for horror movies and Judge Judy. In stark contrast with every other Irish person ever, she’s straight edge. Hello to Jason Isaacs.