“Nothing fun is without sin,” muses Mrs Maguire before a game of bingo in Grantchester episode three and – as per usual – she’s spot on.

Sidney Chambers (James Norton) is SO much more entertaining when he’s being sinful, instead of sulkily strolling around after best pal Geordie (Robson Green), making mournful eyes at forbidden love Amanda (Morven Christie), and depositing large drops of sweat on Mrs Maguire’s (Tessa Peake-Jones) clean floor.

He’s like a little lost Labrador puppy just begging to be petted. And he gets his wish, with some rather, er, heavy petting by the end of this week’s episode, but more on that later. 

Sidney’s not the only one suffering from a serious case of morally enduced lady blues. Leonard’s forcing himself to fall in love with best friend Hilary (Emily Bevan), and when the duo aren’t falling foul of post office robbers, they’re exchanging veiled sweet nothings on the rectory sofa.

Poor Hilary is clearly smitten with her new beau, who’s more determined than ever to live up to Archdeacon Gabriel Atubo’s (Gary Beadle) high standards. If he likes it then Leonard will put a ring on it – as evidenced by that heartbreaking marriage proposal.

Sidney’s not at all convinced that his pal should be playing it straight, and is rather furious when Leonard won’t tell the bride about his previous love, Daniel (Oliver Dimsdale). Leonard fights back, shooting barbs about Amanda at the visibly riled vicar, whose bad mood is rubbing off on everyone around him.

Speaking of Amanda, she’s one strong independent single lady now that she’s nabbed herself a job. Not even estranged husband Guy’s suggestion that the now somewhat more friendly pair get back together can sway her from her plans to strike out on her own. 

In fact, Guy (Tom Austen) even offers to stage his own fake affair so she can escape their marriage relatively scandal free. It’s a welcome change of direction from the former heartless husband, who seems to have turned a positive corner since meeting baby Grace.

A baby, or the thoughts of one, changes Geordie’s life too. Margaret (Seline Hizli) tells him she’s had a scare (much like we did when the pair started bumping uglies smack bang in front of the camera last Sunday night) but thankfully isn’t with child. It’s enough to put the wind up the cheating cad, who realises there’s more at stake than merely losing Cathy (Kacey Ainsworth) and the kids.

He’s not going to give Margaret up just yet, but as he declines to spend the night with the police secretary you definitely get the feeling he’s cooling things down just a tad. 

That doesn’t stop Margaret contributing to this week’s investigation, which involves two mysterious post office thieves. Someone’s been raiding the local establishments in rather curious attire, and to make things more personal for honorary police officer Sidney Chambers, they smacked Leonard up a bit in the process.

The village’s very own Bonnie & Bonnie are eventually caught and their motive for murder and mischief is revealed. Martha (Carlyss Peer) and Wendy (Eve Ponsonby) have both been struggling with the injustice of 1950s patriarchy and were hoping to use their hoard to fund an escape to Paris.

It’s a particularly sad ending that illustrates the young villagers’ struggles with the same buttoned-up fifties morality that keeps frustrated Sidney awake at night.

“This is the life we are here for,” he boldly states during his sermon, “we owe it to ourselves to live it.”

And live it Sidney the-sad-puppy-turned-boisterous-dog-with-a-bone will, scampering over to Amanda’s house, rapping on the door, and resuming their affair with gusto on the stairs. 

Nothing fun is without sin, remember? We can’t help but wonder who’ll make Sidney atone for this one… 

Grantchester continues on ITV on Sunday nights at 9pm