Oh dear. The Musketeers had been carving out an enjoyably undemanding, handsome if predictable storytelling niche for itself. Tonight’s episode was not redeemed simply by there being attractive people and well-shot sword fights in it.

As the Musketeers escort a violent prisoner, the Cardinal’s Red Guards intercept them. This leads to a falling out between the two groups of soldiers, and the Cardinal entering into a wager with the King – who’s better at fighting? The Musketeers need to find cash to have a chance to be the King’s champion.

Meanwhile, Constance’s husband turns up again and swiftly finds out about her affair with D’Artagnan, while Milady meets up with Athos. Meanwhile, Porthos and Aramis are trying to raise funds to join the fighting by wooing rich widows. Aramis – after his displays of sensitivity last week – is shallow and unlikeable here. Porthos gets a brief and genuine relationship, but it ends quickly.

Vinnie Jones – as guest villain Labarge – snarls his threats, gets stuck into his fight scenes, and that’s all the role demands.

When ‘The Challenge’ sets up something potentially interesting, it always plays it safe. Could Treville die, or be seriously injured when he fights? Of course not. Could Porthos’ newfound relationship last and be put under stress by his career? Nope. Will Constance tell D’Artagnan the truth and continue their relationship in secret? Will D’Artagnan – possibly the greatest Musketeer – work out why Constance might perform a total and inexplicable u-turn on their relationship, looking regretful as she does so? Outlook not so good.

There are good moments, though. Constance revealing a handful of money, Treville volunteering to fight in place of his men, the occasional sly smile from the Cardinal, but mainly this is a slow episode full of repetitive fight scenes and contrived situations (secret affairs in the middle of the street anyone?).

On at least two occasions you can work out and say the lines just before the character does. It’s a shame that, after ‘A Rebellious Woman’ set up so much promise (and I enjoyed Susie Conklin’s last episode), ‘The Challenge’ has the feeling of a ticklist, one that was needed to get certain characters into certain places in time for the finale. Sadly it’s not something that the makers have been able to work into an entertaining episode in its own right.

With the finale not far away, D’Artagnan and Constance are now broken hearted, but one is a fully fledged Musketeer apparently impervious to Milady de Winter’s charms (expect that to be tested further), and the other is trapped in a loveless marriage. Porthos is apparently over his lost love, Aramis is still randy, Athos is entering Prime Brood Mode and Treville’s arm will probably be fine by next week.

Aired at 9pm on Sunday 16 March 2014 on BBC One.

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