Guards! Guards!

exploded. The windows blew out. The door left the wall ahead of a great billow of black smoke and sailed into the air, tumbling slowly, to plow into the rhododendrons.
    Something very energetic and hot was happening in that building. More smoke poured out, thick and oily and solid. One of the walls folded in on itself, and then another one toppled sluggishly onto the lawn.
    Swamp dragons shot determinedly out of the wreckage like champagne corks, wings whirring frantically.
    Still the smoke unrolled. But there was something in there, some point of fierce white light that was gently rising.
    It disappeared from view as it passed a stricken window, and then, with a piece of roof tile still spinning on the top of his head, Errol climbed above his own smoke and ascended into the skies of Ankh-Morpork.
    The sunlight glinted off his silver scales as he hovered about a hundred feet up, turning slowly, balancing nicely on his own flame…
    Vimes, awaiting death on the plaza, realized that his mouth was hanging open. He shut it again.
    There was absolutely no sound in the city now but the noise of Errol’s ascent.
    They can rearrange their own plumbing, Vimes told himself bemusedly. To suit circumstances. He’s made it work in reverse. But his thingys, his genes…surely he must have been halfway to it anyway. No wonder the little bugger has got such stubby wings. His body must have known he wasn’t going to need them, except to steer.
    Good grief. I’m watching the first ever dragon to flame backward .
    He risked a glance immediately above him. The great dragon was frozen, its enormous bloodshot eyes concentrating on the tiny creature.
    With a challenging roar of flame and a pummeling of air the King of Ankh-Morpork rose, all thought of mere humans forgotten.
    Vimes turned sharply to Lady Ramkin.
    “How do they fight?” he said urgently. “How do dragons fight?”
    “I—that is, well, they just flap at each other and blow flame,” she said. “Swamp dragons, that is. I mean, who’s ever seen a noble dragon fight?” She patted her nightie. “I must take some notes, I’ve got my memo book somewhere…”
    “In your nightshirt ?”
    “It’s amazing how ideas come to one in bed, I’ve always said.”
    Flames roared into the space where Errol had been, but he wasn’t there. The king tried to spin in mid-air. The little dragon circled in an easy series of smoke rings, weaving a cat’s cradle in the sky with the huge adversary gyrating helplessly in the middle. More flames, hotter and longer, stabbed at him and missed.
    The crowd watched in breathless silence.
    “’allo, Captain,” said an ingratiating voice.
    Vimes looked down. A small and stagnant pond disguised as Nobby grinned sheepishly up at him.
    “I thought you were dead!” he said.
    “We’re not,” said Nobby.
    “Oh. Good.” There didn’t seem much else to say.
    “What do you reckon on the fight, then?”
    Vimes looked back up. Smoke trails spiraled across the city.
    “I’m afraid it’s not going to work,” said Lady Ramkin. “Oh. Hallo, Nobby.”
    “Afternoon, ma’am,” said Nobby, touching what he thought was his forelock.
    “What d’you mean, it’s not going to work?” said Vimes. “Look at him go! It hasn’t hit him yet!”
    “Yes, but his flame has touched it several times. It doesn’t seem to have any effect. It’s not hot enough, I think. Oh, he’s dodging well. But he’s got to be lucky every time. It has only got to be lucky once.”
    The meaning of this sank in.
    “You mean,” said Vimes, “all this is just—just show ? He’s just doing it to impress ?”
    “S’not his fault,” said Colon, materializing behind them. “It’s like dogs innit? Doesn’t really dawn on the poor little bugger that he’s up against a big one. He’s just ready for a scrap.”
    Both dragons appeared to realize that the fight was the well-known Klatchian standoff. With another smoke ring and a billow of white flame they parted and retreated a few hundred yards.
    The king hovered, flapping its wings quickly. Height. That was the thing. When dragon fought dragon, height was always the thing…
    Errol balanced on his flame. He seemed to be thinking.
    Then he nonchalantly kicked his back legs out as though hovering on your own stomach gases was something dragons had mastered over millions of years, somersaulted, and fled. For a moment he was visible as a silver streak, and then he was out over the city walls and gone.
    A groan