What do you get if you cross Pussy Galore’s to-die-for style, Fleabag’s wicked sense of humour, and fierce contempt for the clichéd depiction of women in psychological thrillers like Nikita? Murder, murder, hair!

That, at least, is how executive producer Phoebe Waller-Bridge summed up Killing Eve, a show that follows the increasingly complicated relationship between MI6 officer Eve Polastri (Sandrah Oh) and the Russian assassin Villanelle (Jodie Comer), who she is tasked with tracking down. But what happens when, by the third season, the cat has caught the mouse, the script is no longer blessed with Waller-Bridge-esque witticisms, and the once gripping character arcs are churned out ad nauseam in a desperate ploy to keep the ratings up? A Killing Eve that is no longer killer.

The third season of Killing Eve is such a let down precisely because everything about the first season was so good. From the very first episode, Comer’s portrayal of a character – who is as stylish and flirtatious as she is psychotic and lethal – loudly announced the show’s refusal to comply with the bland stereotypes that women in the spy genre are usually lumped with. Combining an iconically outlandish dress sense, a taste for seducing older women, and a talent for murdering Italian mafia bosses with just a hairpin, Villanelle was, for me, the show’s main draw, blending Bond and Bond Girl without compromising the individual charm of either. Equally convincing is Oh as the frumpy and sarcastic Eve, whose comforting but domestic existence of shepherd’s pie, turtlenecks and bridge leaves her with a bubbling desire for a more thrilling life.

Yet, in the first season, there was another main character, an invisible starring role: Phoebe Waller-Bridge as head writer. Villanelle was the perfect vehicle for her subversive humour, the kind of villain who reassures her psychiatric evaluators: ‘I had quite a heavy period last week, but other than that I think I’m okay’; and her distinctively British banter was perfectly suited to Eve’s ironic wit and deadpan delivery. All three played equally important parts in striking the delicate balance between obsessive and erotic that so electrified Eve and Villanelle’s chemistry.

It might seem surprising, then, that what makes the following seasons so disappointing is not that they are different from the first, but that they are exactly the same. The second season just about managed to get away with it, thanks to careful exploitation of the romantic potential between Eve and Villanelle and an increased wardrobe budget. The third season, on the other hand, with Waller-Bridge long gone, feels drab, worn-out, and, in a word, boring. The attempt to rehash the cat-and-mouse game is lazy and implausible given that Eve has long-since “caught” Villanelle, and the show’s dry humour has become positively parched. I thought I would never say it, but there comes a point where watching Villanelle kill yet another person in a vintage Burberry suit stops being enjoyable.

I’m still determined to like the series. I’ll admit that the portrayal of all the main characters in a more vulnerable light than we’ve seen before is both refreshing and surprisingly moving, and Harriet Walter reinvigorates the cast as Dasha, Villanelle’s new handler. It’s also true that the suspicious death of one of the main characters and the attempted murder of another has set the series up for a potentially explosive finale. But, with most episodes having a miserable ratio of plodding exposition to genuine action, Killing Eve is such a far cry from its former brilliance that, as it nears the end of its third season, it is practically begging for the return of Waller-Bridge.