Most mothers want their daughter’s wedding day to be completely perfect, although few would take it to the extremes that Lydia has. On paper, it looks like a lovely event: a September wedding cruise with friends and family on the aptly named “Perfect Day”. Never mind that the bride is so weary and upset that she can’t get the ceremonial words out, the groom is a simmering mass of frustration, and the groom’s brother is getting louder and louder about how the bride is really meant to be marrying him. Lydia and the ship’s captain are determined to be so cheerful and upbeat that they can conquer all of that.

But no one can be cheerful enough to put Steel into a party mood. He’s particularly grim about this assignment, where the wedding guests have been stumbling through this perfect wedding day over and over again for the last eight years. And all the participants are fully aware of their situation.

Perfect Day plays with several of the basic elements of Sapphire & Steel. Instead of time running out of phase, it’s standing still. Instead of some confused victims and manipulated allies of the breakout, the entire group is not just compliant but complicit. Yet it still has the right feel for an adventure, with a creepy atmosphere and a fierce struggle between the operatives and time. At times the story tips outright into horror, made all the more chilling when contrasted to a wedding – even a wedding more stale than Miss Havisham’s.

Although the resolution is complex to the point of unbelievablity – it’s better just to listen to the exposition and nod, because trying to graph out the explanation will only lead to a headache – the character work is superb. Not only are the members of the wedding party all working with understandable, realistic motivations, the listeners get more brief insights into the operative’s heads.

The usual team is enhanced with the return of Mark Gatiss’s Gold, introduced in the first Big Finish Sapphire & Steel audio. As in The Passenger, he is playing the impetuous specialist who likes to imagine himself as qualified as a full operative. He has a central role without stealing the scenes.

But then, nobody could steal the scenes from Steel. Perfect Day is very much his story, and his fans will appreciate the glimpses behind his usual sardonic grumbling to see just how much he’s willing to do and suffer to get the job done, as his character is both tempted and pushed to his limits – and then well past them.

Perfect Day (by Steve Lyons; starring David Warner, Susannah Harker) was released by Big Finish Productions in April 2007.