Henry had, over the years, made cautious enquiries about his second uncle.
His father, Charles, had been silent for a moment before saying that some things were better explained when Henry was older.
His grandfather had pursed his lips, given Henry a light tap on the back of the head, and told him to go and play.
Taken together, those two responses were themselves a kind of answer. Henry also recalled a particular piece of gossip from his previous life: a persistent rumour that Andrew and Philip were not related by blood.
The British royal family had initially been deeply resistant to incorporating the name Mountbatten into Windsor, and had held that line for years, until 1960, when they had suddenly and quietly compromised.
Andrew had been born that same year. The Queen Mother had still been very much alive and active at the time.
These facts did not necessarily mean anything, but they did sit in an interesting arrangement.
Some things, Henry had decided, were not worth thinking about too carefully.
The further one followed certain threads in the history of the palace, the more complicated everything became, and he had quite enough complexity in his life already.
In any case, this had no direct bearing on him. He had never liked his second uncle, and he was broadly content to leave it at that.
Still, Andrew had spoken to him directly, and pretending not to have heard would be a step too far.
"Uncle Andrew," Henry said, his tone level and pleasant and entirely without warmth. "We're out playing. Would you like to join us?"
Andrew smiled and walked over.
"What's all this?" He looked with evident curiosity at the bottles William and Harry were holding.
"Portable Swamp!" William held his up proudly. "Henry brought it back from his magic school!"
"Magic school." Andrew raised an eyebrow and looked at Henry. "Hogwarts, is it?"
"Yes, Uncle."
Andrew's gaze moved over Henry with the particular quality of a man assessing something he has not yet decided whether to find useful or amusing. Henry met it without visible reaction.
"Interesting," Andrew said. "Can I have a go?"
William handed over a bottle with the generosity of someone who has plenty more.
Andrew took it, unscrewed the cap, and poured the contents onto the ground.
A moment later, a swamp approximately three feet across appeared at his feet. Brown mud bubbled steadily, and a few small plants emerged from it, swayed for a moment, and withdrew.
Andrew crouched to look at the plants more closely and reached out toward them.
At that precise moment, his foot moved onto a patch of ice hidden under the snow. His leather-soled shoes found no purchase whatsoever.
He went over backward with considerable speed.
Henry moved on instinct, not to catch Andrew, but to pull William sideways out of the path of the fall.
William was yanked clear. Andrew was not.
He landed heavily on his back in the snow. The open bottle, launched from his hand by the impact, turned over in the air and distributed its remaining contents across him in a generous and thorough manner.
A second swamp materialised immediately, this one with Andrew at its centre.
The brown mud rose steadily around him. His hair was plastered to his face. His coat, his trousers, and his expression were all comprehensively affected.
Each attempt to stand produced only a deeper engagement with the mud.
William and Harry stared.
Then Harry sat down in the snow and laughed until he was crying.
William was only seconds behind him, bent double with one hand on his knee.
Henry stood to one side. He held out for a reasonable amount of time before acknowledging to himself that it was not going to be possible.
Andrew eventually hauled himself upright. The gelatinous mud coated every visible surface. Several unidentified plant fragments had attached themselves to his hair.
He looked at his three nephews, who were in various stages of complete collapse, and his expression moved through several phases.
"Is it funny?" he asked, his tone darkening.
"Not at all," William managed, between gasps. "Not even slightly funny."
Andrew looked down at himself in silence.
Then he laughed, in the resigned way of someone who has decided that this is the hand he has been dealt and he may as well accept it.
"All right," he said. "I accept defeat."
He looked at Henry, and the particular quality of his earlier scrutiny had shifted somewhat.
"You did that on purpose."
Henry shook his head with complete composure. "Uncle, you slipped."
Andrew held his gaze for a moment, then laughed again, with slightly more genuine feeling this time.
"Yes," he said. "I slipped."
He patted at his coat. The mud, as though it had fulfilled its purpose and was ready to move on, slid cleanly from his clothes and back into the swamp, which promptly vanished with a soft sound and left only a patch of disturbed snow.
Andrew's coat and trousers were entirely restored.
He looked himself over, then looked at the three of them.
"That is quite a remarkable thing," he said.
He turned and walked back toward the house, then stopped after a few steps and turned back.
"Henry," he said. "Next time, don't move so fast."
Henry blinked. "Uncle, I didn't move."
Andrew looked at him without expression, said nothing more, and walked away.
William leaned toward Henry and whispered, "Is he angry?"
Henry put a hand on William's head. "He's not angry."
At noon, Diana heard the story.
She sat on the sitting room sofa and listened to William's account, which had acquired considerable additional detail in the intervening hours. Her expression, as she listened, became gradually more interesting.
"So," she said, when he had finished, and looked at Henry. "Andrew fell into the swamp."
"He slipped," Henry said.
Diana looked at him with steady, unhurried attention. A smile was doing its best to remain suppressed.
"Slipped," she repeated.
"Yes, Mother."
She reached over and patted his hair, then said, very quietly, "Good thing he slipped."
Henry decided he had not heard this.
That afternoon, Charles came out of his study and received his own account of events. His response was the most restrained of all: a single nod, and the words, "Andrew should be more careful where he walks."
Henry noticed, however, that for one brief and involuntary moment, his father's composure failed him entirely.
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