Their expressions, too, told very different stories. May is pictured laughing all the way to her eyes, her head thrown slightly back in a warm, soft cackle. It’s a relaxed, natural pose.

Sturgeon, by contrast, looks less comfortable. She is glancing off to one side like a person forced to spend time with a co-worker she dislikes for a work do, her smile about as warm and welcoming as Loch Lomond on a winter’s day.

But what stands out here are the legs – and the vast expanse on show. There is no doubt that both women consider their pins to be the finest weapon in their political arsenal. Consequently, both have been unsheathed.

May’s famously long extremities – so famous! – are demurely arranged in her customary finishing-school stance. Her knees tightly together, calves at a flattering diagonal, feet neatly aligned. She is classy, the kind of woman whose sexuality is repressed – she is ever the vicar’s daughter, always respectful and anxious not to put a foot wrong. She is the kind of woman who, were she to engage in a threesome with a married newspaper journalist and journalist/MP/professional sycophant, would be prim, eager-to-please, perhaps a little boring.

By contrast, Sturgeon is presenting herself as a temptress, a bad girl who could spice up the  most lifeless of marriages, even those where the couple sleep in seperate rooms and the wife has come to prefer sleep to his dull, lifeless humping. Sturgeon’s short but undeniably shapely shanks are flirty, tantalisingly crossed, with the dominant leg pointing towards her audience.

It’s a direct attempt at seduction: her stiletto is not quite dangling off her foot, but it could be. Imagine if it were. Imagine if she were wearing deep red lipstick and nothing but a silk nightie, blue with the white cross of St. Andrew. Imagine if she were sat on your bed, smiling at you and your husband. Imagine if you could feel something stirring inside yourself that you had thought was gone forever. Imagine yourself feeling torn – wanting to give in to your desires, but knowing there would be dark consequences. ‘Come, succumb to my revolutionary allure,’ she could be saying. ‘You know you want to.’

The message to the Scottish electorate is clear. They have a simple choice: on the one hand the reliable, measured, considerate and cautious politics of Mrs May and the safety of a Union that has endured for 300 years. On the other a wild, dangerous leap into the unknown, a glorious moment of joyful, wild passionate indulgence which could all too easily lead to a lifetime of regrets.