Seven years ago, Dr Charles Runels' lover surprised him at his office, demanding that he inject blood into her clitoris as a Valentine's Day present. She hiked up her dress, hopped on to the exam table and motioned for Runels to put on his headlamp. She explained that she'd been watching him inject his own penis with blood for about a year, and that while his bigger and stronger erections had been fun, she'd grown tired of the one-sided sexual enhancement. It was her turn. So Runels bowed between her legs, numbed her clitoris with an ice cube and shot her up.

"I don't know how graphic you can be with this thing," he said over the phone, pausing mid-story to ask me about the Guardian's policy on discussing orgasms. "But the next afternoon, she came to see me, and her orgasms came more quickly – very strong, ejaculatory orgasms. The passion, the thunder, the sounds that she was making …"

He sighed at the memory.

"That's when I thought: I should try this on my patients."

And just like that, the O-Shot was born.