North American fans of the BBC's re-imagined Robin Hood will be pleased to learn that the third season is now available on dvd  in a five disc set with over an hour of bonus material, including behind the scenes features, character profiles, video diaries and more. As most will know, this is the final season. The axe fell in July 2009, disappointing many and leaving others wondering what the fuss was about. From the outset this retelling of the Robin Hood legend divided audiences, many enjoying it for its over-the-top sense of fun and its modernity, others dismissing it for having implausible story-lines and for introducing modern concepts outrageously out of joint with the twelfth century setting.

The show's creators, Dominic Minghella and Foz Allen, make no apologies for its modernity (although some critiques clearly think they should), and would no doubt argue that it was intended for a young audience in any case. If so, it was right on target for a demographic that is generally less critical or at least more forgiving: Robin Hood was a ratings success and even though numbers were on the decline, they were rarely less than respectable, and the show remains one of BBC Worldwide's best sellers.

Cast departures at the end of season two and the decision of Jonas Armstrong (Robin Hood), Richard Armitage (Guy of Gisborne) and Keith Allen (Sheriff of Nottingham) not to return for a fourth season, meant that the writing was on the wall however. A fourth season was considered, and Archer, a previously unmentioned half-brother of both Robin and Gisborne, was pulled out of the hat in episode 10 (Bad Blood), with the clear intention that he step into Robin's buckskin boots when they were vacated. But the powers-that-be at the BBC were not convinced that the show had a future without Robin Hood and plans for the fourth season were dropped.

Which leaves us with three seasons to look back on fondly. Or not.

The third and final season kicks off with great promise. It's intense, fast-paced and focused. Robin and what's left of the gang of outlaws return to England from the Holy Land with the memory of Marian's murder by Gisborne burning fresh in their hearts. Robin's blackened heart is set on revenge, all else forgotten. He abuses his men, dismissing them, and confronts Gisborne in a fight to the death which ends with Robin's unlucky defeat.

But Robin's survival is guaranteed by an absurd turn of events. Rather than making certain that his defenceless enemy is killed by a sword thrust to the heart, Gisborne opts to throw Robin off a cliff into a river. Naturally, the hero survives.

It goes without saying that Robin can't die yet - it's only the first episode of the season! But what this incident demonstrates is a failure of imagination by the show's writers to develop a more convincing story-line to track Robin's loss of direction and eventual rediscovery of purpose. It's entirely a consequence of bad writing that Robin is placed in a situation that requires an act of stupidity by a man who should know better (after two seasons of trying to kill Robin). If Gisborne is characterised by anything, it is this: he is a ruthless and effective killer of the vulnerable. And yet when he has his mortal enemy at his mercy and every reason to kill him, he fails to do so.

The next seven episodes in season three are more of the same. Implausible incidents stacked one on top of the other.

Clearly I'm not a fan of the show, although I wanted to be. I watched season one when it first ran and find two seasons later that my negative assessment of the show is unchanged and for the same reason: too often the writing is awful. Given Dominic Minghella's involvement with the comedy-drama Doc Martin, which is deservedly recognised for the high quality of the writing, it's peculiar that the Achilles heal with his Robin Hood is in fact the writing, some of the laziest of any series in recent times.

Where to start? Well, there's the use of such tired clichés as a solar eclipse to awe the people and save the day (episode one). Solar eclipses might be rare events, but they always seem to occur at the most opportune moments, or at least whenever a writer runs out of original ideas. Then we have central female characters who are always feisty, independent anachronisms, and are always already trained in the martial arts whether they are peasants or nobles. Speaking of utterly ridiculous anachronisms, my favourite in season three is Brother Tuck's moment of Gandhi inspired stupidity when he convinces a group of peasants to sit passively in front of the Sheriff's notoriously brutal troops in an act of non-violent resistance. This is the very same group of peasants which previously defied the Sheriff and which would probably be executed anyway if they were caught.

And last in this brief list of examples of uninspired writing, just six episodes into the season - a short while after Robin was ready to give up everything in order to avenge the murder of his beloved wife, Marian - he has a new love interest. Surely a very cynical assessment by the writers of the values and interests of the target audience.

Far worse however is the development of story-lines based on implausible and illogical incidents. Too often it appears as if the end of an episode was imagined first and then the writers set about finding some way, no matter how implausible, to bring that ending about. A good indication of this is that if the plot requires Robin and company to be captured, they are captured in the most ridiculous ways. If not, they're untouchable. Any number of examples could be picked to demonstrate this, but one will do: in episode seven, Robin and his current love interest, Isabel, walk together through Sherwood Forest when Gisborne sneaks up behind them and slaps a pair of handcuffs around not one but both of them! How on earth has Robin Hood managed to elude capture all these years?

I could go on.

Some defenders of the show argue that it's not meant to be taken seriously, but it's more accurate to say that the show can't be taken seriously. In anycase, I doubt that Minghella and Allen would be happy with such a defence: it's clear that despite the over-the-top action and pantomime acting of Keith Allen as the Sheriff, the show was always intended to tackle serious contemporary issues such as national security, terrorism, human rights, equality of the sexes, and so forth, at the same time that this is a story about the fight against tyranny and injustice, one that involves murder, revenge and brutality. Far from light-hearted concepts. Unfortunately, these serious issues are dealt with in story-lines that have more implausibility than a White House dossier on the existence of WMDs in Iraq and that is less a consequence of intention than bad writing.

To be fair, the last four episodes of season three are head and shoulders above the rest and it's fairly clear why: the writers have four episodes left to deal with Robin and Gisborne's death and to set the series up for a potential fourth season. Finally just as I was about to dismiss the show as something that only an uncritical young audience could enjoy, the writers put their thinking caps on and did their job. I was entertained.