"Harriet," said my Master softly, "why don't you introduce yourself?" Because it would be too humiliating, I thought to myself; because I couldn't bring myself to look into the eye of this stranger; because now he had seen every inch of my body except for that which he would normally see first, my face, and for me to expose that now would be almost as shaming as flaunting my naked body to strangers in any other circumstance. I sat, immobile.

"Harriet," my Master repeated testily. I knew there was no escape, knew that my indignity was complete. Resignedly, I scratched at the panties masking my face and slid them over my jaw, letting the couple of inches of soaked crotch spill out of my mouth; I pulled them over my eyes, blinking in the direct sunlight, and with a flourish which scarcely represented my feelings I lifted them clear of my head and dropped them onto the bench.

I knew that I had been exposed to the stranger for some minutes, in the most lewd and revealing fashion imaginable, but now, now that my face was revealed to him as well, now that I was no longer an anonymous body but a real, identifiable person, my humiliation was increased a thousandfold. I blushed furiously and looked resolutely at the path in front of me, incapable of looking the stranger in the eye.

"This is the third time I've had to ask, Harriet," my Master said in an ominously even voice. I galvanised myself and looked up, into the eyes of the stranger.

"Hello," I said. "I'm Harriet, pleased to meet you." The stranger smiled palely, clearly baffled by the scene in front of him. He looked like he was about to run away, and I can't say I blamed him: this was too freaky for words. He was late fifties, maybe early sixties, mostly bald and with a stoop which I think was permanent and not just borne out of the shock of his discovery. He had friendly features, a warm, lively face, and in different circumstances I think I could have taken to him.

"Since you've caught Harriet in flagrante, I think probably the ball's in your court," my Master said to him. The stranger continued to look perplexed, clearly not understanding what he was implying. "Obviously," my Master explained, "we'd be keen that this went no further. We'd hate to have the police involved, or anything like that. But we're not in a particularly strong position to negotiate. If you felt strongly that that's what you should do, we couldn't really stop you."

The stranger looked embarrassed, and I think he was about to say he had no intention of reporting us when my Master continued.

"But perhaps Harriet could do something to persuade you?"

There was silence while the stranger digested this. He looked at me and gulped, almost comically, like Shaggy in Scooby Doo. Despite myself, and despite my predicament, I smiled.

"I don't think so," he breathed hoarsely.

"Anything you wanted," continued my Master. "Name it."

The stranger looked edgily around him, clearly anxious not to be discovered in this unnatural scene. I could tell from his eyes that he was tempted, but fear was overtaking desire, as it often does in people who won't let themselves go. It's what separates people like me from the crowd: an ability to let impulse rule reason. I knew that if I left the decision to him he would walk away. Stretching forward, I ran my hand down his thigh and grabbed his large, rough hand. I held it for a moment, applying no pressure, waiting for confirmation. He squeezed it and I knew. My Master had willed me to do this and so I had no option but to go through with it, no matter how I felt about it. I looked at my Master and he nodded. Bowing my head, I obeyed.

I pulled the stranger on to the bench and he sat stiffly beside me, his head swivelling, looking all around for signs of imminent discovery. He needn't have worried: apart from the footballers, engrossed in their game, there was nobody around. I stroked his thigh, turning and resting my naked leg against him. I pressed in closely, hooking my arm round his back, my breasts wafting gently against his jacket, my head bobbing seductively beneath his.

I took his hand and pressed it to my breast, feeling him grip me tightly, experiencing for the second time that day a frisson of excitement as a complete stranger mauled at me. I hooked my ankle over his right knee and pulled, spreading his legs a fraction, then settled my hand on his crotch. He was hard. Licking my lips, I began to stroke gently, rubbing my palm against the fabric of his trousers, tracing the outline of his dick with my fingers.

In truth, I had no great desire to touch him, but I was performing now, obeying my Master, doing as instructed. I fumbled with his zip and eased it down. Fishing inside, I eased my fingers onto his underpants and felt the rigid shape of his cock through them. He seemed fairly large, surprisingly so, and I gripped him firmly. I unfastened the button of his trousers and they opened in front of me, allowing me room to manoeuvre his knickers out of the way. I gripped the waistband and lifted it up and over his cock, resting it beneath his balls.

"Mmm," I said encouragingly, as I took it in my fist and squeezed. He sighed and leaned back, his head pointing skyward. I began to wank him, rolling my palm over his length, rubbing it against his circumcised head, squeezing it until a drop of pre-cum emerged from his little slit. He was squeezing my breast harder and harder as excitement overtook him, and I guessed he would not take long. I grabbed his other hand and pulled it to my thigh, allowing him to work his fingers up towards my pussy. It would do nothing for me, I knew, but it would satisfy him. His fingers worked roughly against my slit, sliding immediately as deep inside me as he could manage and probing almost gynaecologically.

I set up a regular rhythm on his cock, twisting backwards occasionally on the downstrokes to apply extra pressure. I wanted this to be over as quickly as possible. I had already been discovered twice today, and I had no desire for a hat-trick. I pumped furiously, feeling my actions mirrored by the activity of his hand pounding against my pussy, and squeezed his cock as hard as I could. My hand was aching, but I was rewarded after a couple of minutes when the stranger went rigid and stopped what he was doing with his hands.

I didn't want to cover him in his own come, so I bowed my head and fixed my mouth around his dick. I pumped him again, and after a matter of seconds a spurt of hot come flew up into my mouth, followed by another, and another, a steady stream of fluid pulsing into me. Swallowing, I continued to wank him until his cock stopped spasming, then licked his head clean. I sat back and stared at my Master. He smiled.

Almost instantly, the stranger began to cover himself and mumbled something indecipherable. He steadied himself, rose from the bench and with an embarrassed nod disappeared in the direction he had come. I didn't even know the name of the man whose come was dripping down my throat. After the event, of course, comes the guilt, and he was no doubt as ashamed of what he had just done as I had been when I was first discovered by him. I was glad to have been of service to him, but I doubted whether he had enjoyed the experience as much as he might have done, had he only been able to let himself go.

"Well done, Harriet," my Master crooned. "But now, I'm afraid. It's time for punishment."

I stared, open-mouthed.

"You remember? From this morning? I promised you a spanking later on."

"Not here?" I cried.