Sherlock turns out to be a size queen – who knew? But I couldn't leave him high and dry, could I? He has to get his just 'desserts'! Verityburns, as far as I know, is the originator of the expression 'liquid sin', but I loved it so much, I had to borrow it. Credit where it's due – which should also go to Messrs Gatiss and Moffat, and of course, Conan Doyle, for the splendiferous gorgeousity that is Sherlock and Watson. I don't own any of it. I wish I did.

Since when did the navel become a sexual orifice, Sherlock wonders, as John tongue-fucks his belly button. There certainly seems to be a direct electrical connection between his navel and his genitals because that thrusting tongue is sending shocks right down the core of his cock, and Oh, Jesus, that is sweet.

They are in John's bed, to which Sherlock half led, half carried his sex-shocked lover after their bathroom encounter. He lowered John into the sheets and kissed him, long and slow, until his heart rate calmed and his eyes began to focus again. Since then, John has been working on Sherlock's belly like a man possessed. Its heaven.

But then he stops, and Sherlock is subjected to a surge of disappointment as he wriggles up until he can look down into the detective's eyes.

'What do you want, Sherlock,' he whispers. His voice is liquid sin.

He looks down over Sherlock's body, hungrily. Sherlock, though, is transfixed by the look on his face, hard and yet soft, utterly implacable, totally debauched.

'Whatever you want.' Those beautiful eyes have turned that indecent indigo again. Sherlock understands what he is saying, what he is offering, but he can't take it.

'No,' he breathes. 'I can't. It has to be you, John. Only you.'

'Then what?' John kisses his neck, nips it gently, sending thrills down Sherlock's spine. 'Whatever you want, my love, just say and I'll do it to you.'

Sherlock finds he is shaking. He has been fantasizing about this moment all week, but now it comes to it, he finds his cheeks are burning and the words won't come out of his mouth. John smiles down at him.

'Come on, after what you just did to me, you can't be shy!'

'No, it's just-'

'Tell me.'

Sherlock has to close his eyes because he's too embarrassed to look at John when he confesses what has been in his mind.

'I want to ride you,' he breathes. 'Bareback.'

There is silence. Sherlock opens his eyes to find John is staring back at him, and is amazed to see there is shock in those rounded features.

'Seriously?'

'I want to feel you come inside me. Naked.'

John just stares.

'I don't know why it's so important. It just is. Besides, we both know we're safe. You've had no scruples coming in my mouth up until now, and you haven't been bothered when I come in yours-'

John just keeps on staring down into his eyes.

'John? Please say something?'

Then he realises it is not fear that has frozen the little man, but emotion. He had not comprehended the ramifications of his fantasy until now. The fact of dispensing with condoms means surrender to complete trust.

'You really want this?' John's voice finally comes out, gruff with tenderness.

'Yes.'

John kisses him hard, with more passion even than that first turbulent night, as if he is channelling his whole soul into his lips. Sherlock knows there will be no more discussion. John has given up everything. No more rules, no holds barred. This is love.

'Open me,' Sherlock whispers.

John pushes him over onto his belly. The contact of cotton sheet against agonised erection is intense and he groans helplessly, raising one knee to lift his pelvis a little. John starts kissing the back of his neck, making his hair stand on end deliciously. That narrow-lipped mouth works the skin, licking and kissing, gnawing on the projection of a shoulder blade, while fingertips stroke over his tender sides. John reaches down, caressing the backs of Sherlock's thighs, tracing little circles on the backs of his knees, so that he shivers with bliss. He kisses and licks all the way down Sherlock's back bone until his reaches the round globes of his backside, and then sinks his teeth in. Sherlock gasps and moans.

John is obsessed with his pert bottom, Sherlock realises. He kisses and nips and rubs and it is utterly wonderful. The detective feels like his cock will burst or drop off with the tension, maybe both. His balls hurt.

'Please, John,' he whimpers, even though that whole buttock-sucking thing he is doing is so thrilling.

John grips his hips in response, lifting Sherlock onto his knees and spreading out the long legs. He strokes the skin again, hips, thighs, bum, almost with reverence. Sherlock is just expecting a finger when instead he feels a squirming tongue, and he jumps with the shock of it. John licks a circle around his anus and then begins to press deep. That wonderful, slippery insertion! Sherlock's head is spinning. John is doing what he did to Sherlock's navel, and the detective's legs start to shake uncontrollably. He is panting now as John's hand slips between his legs and grasps the blood-weighted shaft.

'Not yet! God! Not yet!'

The hand withdraws reluctantly with a little tug of foreskin that forces a groan from both their lips. Instead, slick fingers replace the wriggling tongue, scissoring, twisting, opening. Sherlock can't help but press back against them. He has no idea how much longer he is going to last, and if John brushes his prostate just one more time – no, think, Sherlock think! He starts reciting the numerical value of Pi to as many decimal points as his fogged brain can recall, fighting to concentrate as John slips a third finger in and starts to fuck him with it mercilessly.

'Oh, God, now!' he cries out.

The doctor flings himself onto his back, and Sherlock crawls onto him, lowering himself down. He feels the pressure in his entrance, steels himself to concentration and relaxes his inner muscles. And bears down.

John moans.

It is incredible. Not the rubberised slither of before. Now he can feel every vein and rib against his sensitive sphincter as he pushes deep, taking it all, every last damn inch, higher, higher, and then lifts off and takes it again, and oh, my, God, it is incredible.

'So good…. So good….'

John's hands slide over his skin, his throat, his breast, his belly, his thighs. He pinches at Sherlock's nipples, twisting the hard brown nubs. He goes to grasp Sherlock's shaft, but the man on top can't bear it and bats his hands away.

It is so deep, so intense, this fucking. And now John is shaking with need, his hips thrusting under Sherlock, unable to hold himself back. Sherlock pumps his pelvis up and down, knowing there will be bruises later, knowing he will probably be barely able to walk for a week after this, this great hunk of meat ramming into him, and who the hell cares anyway because this is his John, his wonderful John, taking him and marking him and possessing him, and nothing, but nothing else can ever be as good as this.

Pi has reached thirty-seven decimal places when John grabs him and rolls. Suddenly Sherlock is on his back, being royally fucked, his cock bobbing and chafing against John's hairy belly. Frantically he grabs his own shaft, grips it, feels the tension begin to break, and then he cries out:

'John! John!'

A wail of love and desire.

And then something shifts between them, and they cease to be frantic, desperate. An erotic calm blankets Sherlock's heart. Face to face, they enter another realm, a place of surging emotion, too profound for words. Their bodies move, meld, became something else, a third being with a shared heart, and when they come, they come together, as one, wordless and silent, with tears flowing down their cheeks.

'I love you,' Sherlock says later, lying on his back, John panting beside him. 'I've loved you from the first moment you walked into the lab at Barts with that ridiculous stick of yours. And I know that I will be in love with you for the rest of my life.'

Oh people, I am not finished yet…. Stay tuned!