Gavin hated having to stand on a crowded tube in the rush hour, and this one was particularly jam-packed. To make matters worse, he’d had a seat at one point, but had gallantly surrendered it to an extremely pregnant woman who’d got on at Chancery Lane. Since then, the train had got increasingly crammed, until he was now crushed into a corner with his crotch pressed awkwardly against the buttocks of a slim, professionally-dressed woman who was hanging from one of the straps by the door, facing away from him. The top of her head was just level with his nose, and he had to admit that her blonde hair did smell very agreeable, but even so he didn’t particularly want it up his left nostril.

But the worst of it was that a combination of the heat, the movement of the carriage, and the pressure against his crotch meant that he could feel himself starting to get an involuntary erection. “Oh fuck,” he thought, “What must she think? She’ll assume I’m one of those perverts who gets his kicks out of frotting himself up against women on tubes.” Gavin had read an article about this very issue in the Standard only the other week, and the Mayor of London had been quoted as saying that he hoped the police would be imposing much stiffer penalties against this sort of thing in future.

The penalties weren’t the only stiff things Gavin had to worry about. Every time the train shook, the woman’s firm cheeks pressed against his bulging crotch, and he felt his erection getting larger and larger. He tried to ease himself further into the corner, but the woman’s rump stayed resolutely lodged against his shaft. To make matters worse, he was wearing thin trousers, so there really wasn’t much between his throbbing rod and her posterior.

His penis felt fully erect, and yet as it pressed resolutely against the woman’s cheeks it crossed Gavin’s mind that she hadn’t yet turned around and slapped him. Surely she must be able to feel it rubbing against her firm, rounded bum? Maybe she just thought it was the corner of his briefcase.

He looked down, and a tingle of excitement raced through his body. He could see that the woman was unmistakably rotating her cheeks against his substantial trouser-bulge. Not only was she perfectly aware of the situation, she was actually enjoying it, the little minx. Gavin wondered if he should say something, but then decided that might spoil the moment.

Experimentally, he pushed gently back against the woman, manoeuvring the beast in his trousers against her. Gratifyingly, she responded by pushing back against him harder, by chance finding just the right angle to stimulate the sensitive rim of his cock-helmet. He was now firmly wedged into the corner of the carriage, which meant that she could grind against him as hard as she liked.

“Oh fuck:” the words slipped out under his breath. He began to rub his erection harder against her, as she pressed back. It was definitely a two-way effort now. He heard her gasp, just a little bit, as his shaft slipped into the cleft of her buttocks, finding the ideal spot.

Effortlessly they slipped into the perfect rhythm, rocking against each other in time with the train. All too soon he felt himself approaching the point of no return. If he didn’t stop now, pull away, he’d be unable to stop it.

A little gasp escaped from him as he pressed even harder against her, almost knocking her off balance. But she caught herself; pushed back firmly; and his heart missed a beat as he felt his semen start to travel up his shaft, unstoppable now. Then he came, harder than he’d come for a long time, his semen spilling into his trousers in a series of spurts of hot sticky mess. Even more embarrassingly, the strength of his ejaculation caused his semen to force its way out through the thin material of his trousers and smear itself all over the back of the woman’s skirt as she pressed against him.

He glanced down and could see the enormous sticky patch spreading across the front of his trousers. He could smell it too, the unmistakable scent of fresh semen wafting up to his nostrils; surely everyone else around them could smell it too?

The woman’s skirt was coated in it, a Rorschach blot of fresh semen spread right across her buttocks, soaking into the material. Quietly, she let out a long sigh, as with perfect timing the tube drew into Notting Hill Gate. A tsunami of people burst out onto the platform, and the woman allowed herself and her spunk-stained skirt to be carried away with them, disappearing towards the exit without even turning her head.

Gavin leant against the door, breathing heavily, while holding his briefcase casually across the sticky front of his trousers. He anticipated an uncomfortable ten-minute walk back to his flat in White City as the gooey semen cooled in his trousers, but he knew he’d never forget his unexpected encounter. He felt sure she’d remember it too.