Looking at Rob Brydon as the genial host of Would I Lie To You?, you might never have guessed that he made his name co-writing some of the darkest, most original comedy ever produced by the BBC. Julia Davis, however, is synonymous with skin-crawling comedy. But to call anthology series Human Remains (2000) simply 'dark' would be to do a disservice to the incredible work they exhibit both as actors and writers.

In the late 1990s, Brydon was a presenter of a very different kind: he worked as a salesman for a shopping channel. Desperate to break into comedy, he recorded several characters on a tape that he passed onto his old school chum Hugo Blick, eventually ending up in the hands of Steve Coogan. The production company Coogan co-founded, Baby Cow, would go on to make both Human Remains and Marion And Geoff (2000 - 2003) a one-man series pivoting on the monologues of eternal optimist Keith Barret. Much like the characters in Human Remains, the audience learns far more about Keith from what he doesn't say than from what he does.

Davis, meanwhile, was already making a name for herself in the comedy world, writing sketches for Radio 4 series Five Squeezy Pieces with Arabella Weir and Meera Syal. Through this she met Graham Linehan and Arthur Mathews, which in turn led to her being cast in Big Train. A tape of her characters also ended up being seen by Coogan, who invited her to write and act in his 1998 tour The Man Who Thinks He's It.

Brydon and Davis met at an improvisation group, and improv would turn out to be an important aspect in the development of Human Remains, because the way in which it was written is unusual - Brydon and Davis set up a camcorder and improvised in character. The footage is available on the DVD release and is a fascinating insight not only into their creative process, but also into the friendship between the two. One of the greatest joys is watching Davis cracking up as Brydon goes in a particularly unexpected direction, then five minutes later Brydon doing the same as she surprises him.

The main thing to take away from this is that it meant the scripts were, in essence, being rewritten before they actually put down a single word, the recordings enabling them to pick out the funniest lines and craft them into the finished scripts. The other result of this process is that each character is so well developed and the acting so underplayed and naturalistic that watching them on screen you forget that they are all just Rob and Julia. In the commentary, the pair discuss in detail how a lot of the character dynamics were developed from the idea in improv that each relationship should be based on status; one or the other always having high status with power over the low status of the other.

This is exhibited perfectly from the very first episode. An English Squeak follows Peter Moorcross and Flick, an upper class man-child and his not-so-disabled wife. The tone is set from one of the first lines, where Flick says "I think having a husband is a little bit like having a pet. Certainly, Peter is that, in that he's always around and getting under my feet. One sometimes wishes one could put them outside, but one does have to keep up standards".

In each episode the audience discerns far more than the characters give away through dialogue. As the story unfolds we see Flick is emotionally abusing Peter, denying him sex (because, according to her, the illness means that "penile accommodation is absolutely impossible", later saying "Peter, I am tired and I am tight!"), while sleeping with other men herself.

It's important to emphasise that the darkness permeating these scripts is not something used purely for shock value. Rather, Brydon and Davis use dark themes to further explore the inner lives of their characters. All Over My Glasses, for example, is on the face of it an absolutely horrific tale of domestic abuse, as we witness thuggish yob Stephen physically and emotionally hurt the sweet natured Michelle, who may or may not have some kind of mental illness - one particularly harrowing scene sees Stephen violently grab and shake the pregnant Michelle while saying "Take the baby to Alton Towers!". But within that framework, comedy comes from Stephen's heavily repressed homosexuality, and, even with no dialogue, Ruth Jones and Mark Benton manage to create characters with whom we sympathise.

All this might make it sound as though Human Remains is a slog to sit through, what with the numerous references to violence, sex and repressed emotion. In fact, the gag rate is incredibly high, with many of the jokes being throwaway comments you only catch upon a second viewing. In Slither In for example: "Ignorance is bliss. That, to me, is the beauty of a coma." This is arguably the most upbeat episode of the series, with sex positivity and a couple who genuinely love each other. That said, they do decide to expand their sex dungeon into their comatose sister's bedroom and the episode ends with them covering the sister in a dustsheet as work gets underway.

Hairless, which follows musical duo Fonte and Barne, is a study in sexual repression and the male ego in a deeply unhappy relationship. As Barne describes it, his hobby is "self-relief... I'm harming no one, as long as you're not in close range!"

More Than Happy, meanwhile, may well be the bleakest of all, dealing as it does with a couple who lost their children and are dealing with intense loneliness and depression. The episode's title comes from the moment where Les asks wife Ray "Are you happy?" to which she, looking near suicidal, says "No". His response? "Yeah. You're more than happy."

It is ironic that ostensibly the most 'normal' of the couples, Tony and Beverly in Straight As A Flute, actually turn out to be the nastiest. Vicious, vindictive and all under the cover of hosting religious meetings: "If Church is your vaccination against Satan, these meetings are your boosters". Sexual proclivities are once again front and centre, as Tony comments "As I always say, try it once, and if you don't like it, we'll come back to it in a few nights". In their own way, though, they are one of the most loving couples, with Brydon calling them "harmonious in their unpleasantness".

Matt Lipsey, who directed all six episodes, also deserves a lot of the credit. The documentary style, the shots that linger far longer than is comfortable, the way the camera catches moments that weren't meant to be seen. Lipsey has gone on to direct other dark-edged comedies like the entirety of Psychoville and episodes of Inside No. 9 to great acclaim.

The DVD of Human Remains is well worth adding to your comedy collection, as it might just be one of the most comprehensive releases of a cult comedy ever. Not only can you see the improvisations that are the anthology's genesis, but there are also commentaries from Brydon and Davis, an extra mini-episode following Fonte and Barne on tour, out-takes, deleted scenes, trailers and a compilation of Les's songs.

After Human Remains, Davis appeared in a number of comedies with Chris Morris, including Jam and Brass Eye, but she concentrated mainly on solo projects, creating one of the most horrific monsters ever to grace the small screen in the form of the sociopathic Jill Tyrell in BBC Three's Nighty Night. Hunderby, Camping, the pilot Lizzie And Sarah and Sally4Ever all delved even further into the depravity hidden behind the delicate fabric of society, More recently, Davis launched a musical duo called Sybil with actor and director Mercedes Gower.

Brydon also went on to star in an eclectic range of projects, including Annually Retentive, a satire of panel shows, the terrific Director's Commentary and Supernova, later finding huge success playing an ego-fuelled version of himself opposite Coogan in The Trip.

However, whilst they also appeared together in Gavin & Stacey, the greatest shame is that Brydon and Davis haven't collaborated on a writing project again since. Brydon said in an interview with The Telegraph in 2020 that "It niggles away at me. I'm always talking about it. Steve's always telling me to do more character stuff. Julia and I have innumerable lunches where we discuss ideas. I would still like to do that sort of thing - I'm sure I will at some point. We have improvised tons of stuff in the intervening 20 years and written things. We've got hours of tape."

So here's hoping that this happens sooner rather than later, because Human Remains is the benchmark by which all boundary-pushing comedy should be measured. The thought that Brydon and Davis may one day decide to unleash more characters onto the screen is very, very exciting.