Arthur turned over and sat up. 'There are some things you should know about me,' he said, and his voice sounded bleak now, far from the voice of the man who had been reminiscing lovingly a few minutes earlier about his favourite hawk. 'First of all, I'm a bastard.'

'So are plenty of the knights here.'

'I'm the result of rape.'

'Oh.' Guinevere sat up as well, so that she could look him in the eye, taking in the seriousness of this. 'It's not your fault how you came into the world,' she reminded him, taking his hands in hers. 'What matters is what you do once you're here.'

'I know. I'm going to come to that. But first I have to explain this. My father lusted after Igraine, the wife of Gorlois the Duke of Cornwall – who had been one of his most loyal allies until my father until my father started making advances against his wife. So my father besieged the two of them, while they were each defending one of their two castles, and – this is the horrible part – Merlin disguised my father as Gorlois and placed him in Igraine's castle, to trick Igraine into agreeing to have sex with him, while my father's soldiers killed the real Gorlois. And she got pregnant with me. Afterwards, when she found out the truth, my father forced her to marry him.

'I don't know what it can have been like for her, but it can't have been a good home for any child to grow up in. Gorlois and Igraine's three daughters, who were teenagers when this happened, got married as soon as possible to get out of the house – the older two left home out almost at once, and Igraine asked the king to let Morgan go to boarding-school until she was old enough to get married. And when I was born, Merlin didn't think it was a safe home for me to grow up in, so he took me away, and turned up at the most remote castle he could find, dressed in rags like a beggar, croaking out that he'd found this unwanted baby lost in the woods, and would the master of the house have mercy and take the child in and give him a good home? And then, as far as I can tell, he moved into a little cottage in the forest, near enough that he could keep an eye on me, and when I was nine and met him in the forest, he offered to be my tutor.'

'It still seems hard to believe,' said Guinevere. 'I mean – this is Merlin we're talking about! The man who taught you and Kay about justice, and why it's wrong to start wars, or to treat war like a game. I can't imagine him enabling a rape.'

'I don't know,' said Arthur. 'I can't imagine what it must be like to be Merlin, and know what's going to happen without being able to stop it. Years before he met Nimue, he told me that he was going to fall in love with a lady who was going to trap him under a rock forever, but he wasn't interested in avoiding her, because he knew that it would happen. And he didn't say why she would want to lock him up, so maybe he foresaw that he was going to behave badly to her and she'd want to get rid of him.

'I think maybe he did feel guilty about what he did to my mother, though. Maybe that was why he left King Uther. And I can see why he never talked to me about who I was, at least when I was a boy. He didn't want me to know that I was a prince until the time was right, and he didn't want me to feel guilty about being born. And he never told me I had sisters. Even when the outlaws who lived in the forest asked Kay and me to help them fight someone called Morgan le Fay who was possibly a fairy or a witch or the daughter of the Duke of Cornwall, and when we came back bringing the prisoners we'd rescued from her and carrying the head of Morgan's griffin that Kay had shot, Merlin never told me that Morgan was my sister. She'd made herself look like a fat middle-aged woman with a moustache, who lived in a castle made of food, though I suppose she'd have been in her early twenties – maybe younger than I am now. But I suppose it didn't matter then – though I'm glad we didn't kill her.

'But then, later on, when I was king, and I met Morgause, the Queen of Orkney, Merlin didn't tell me she was my sister, either. I don't think that was because he was worried that it would change history if he did tell me. He was just confused from all the time travel, and he knew there was something important that he hadn't told me, but he couldn't remember what it was.

'But as for what I did – it doesn't sound very different from what my father did. I had been at war with her husband, King Lot of Orkney – mainly because Morgause wanted him to fight me because she wanted to avenge my father's death – and I'd defeated him. And then, just a few weeks after the war, Morgause came to visit me, in my castle.

'I don't know how it happened. It was the night after King Pellinore's wedding day, and it had been a wonderful day and we'd all had a great time. It was the first time I met young Lancelot, or Galahad as he was then, when he was a young page. He was the son of King Ban of Benwick, one of my allies, and he won nearly all the games that we'd organised for the children, and afterwards we had a very serious conversation about whether he wanted to be a knight when he grew up, and whether he wanted to come and join me as one of the Knights of the Round Table. He was a very serious boy, even then, and he grasped the idea of founding an order of good knights to put an end to bullying and the rule of strength much more quickly than I had. I thought that I'd like to have a son like him, some day.

'Anyway, I went to sleep that night, wondering what it would be like to get married and have children, and thinking about what Merlin had told me about how I was going to marry a queen with black hair and blue eyes, and I woke up to find a stunningly beautiful queen with black hair and blue eyes standing by my bed, with her four children behind her: four boys, the oldest a couple of years older than Ban's son and the youngest a couple of years younger, all with red or blond hair but blue eyes like their mother. And I had something tied round my neck in a bow – a long, soft tape made of some sort of skin, as far as I could tell.

'I didn't know how I knew, but I remember – I felt convinced that she was my wife, or that she was going to be my wife, and that we loved each other and had always been together. She told the boys to clear off, and they filed out through my bedroom door without saying a word. They looked frightened of her and in awe of her and relieved and disappointed, all at once.

'As soon as they'd closed the door, the woman took off her crown and her dress, and then took my nightshirt away from me – but very carefully, so as not to disturb the thing round my neck – and climbed into bed with me, and…'

Arthur fell silent. Guinevere put her hand on his, then removed it, fearing that she might remind him of his seducer. Arthur pulled her to him and hugged her, nuzzling her neck while she stroked his golden-haired head. After a long time, he found the words to go on with his story.

'It was – strange. I was a bit clumsy at first on our wedding night, like a boy practising running with a spear for the first time, but on that night years earlier, I instinctively knew what to do, as if it was a dream. I don't recall her physically guiding me, but – somehow my body knew what to do. It was easier than finding out how to swim or fly when Merlin turned me into a fish or an owl.'

'It sounds like magic,' said Guinevere, not romantically but sympathetically.

'I'm quite convinced it was. It all seemed normal and right, until her second-oldest son rushed back into the bedroom and tried to throttle me, and his mother pulled him off me and beat him. But when the boy – Agravain, though I didn't know his name then – had grabbed at my neck, he'd pulled the thing from around my neck, and suddenly it was as if I'd woken up and I could see that all this was wrong. I couldn't understand why I'd suddenly had sex with a stranger when I wasn't even…' he tailed off again.

'I'm sorry,' said Guinevere, after it had become clear that Arthur didn't want to continue. 'I knew something bad had happened to you, but I didn't realise it was that bad. You do realise that it wasn't your fault, don't you? Any more than what happened to your mother was her fault.'

'That part wasn't my fault, no,' said Arthur miserably. 'What was my fault was afterwards. Merlin was away on holiday at the time, but when he came back, he told me that the woman who had – seduced me had been my sister, and that she was pregnant with my son and going to give birth to him on the 1st of May, and that he was called Mordred and was going to grow up to be my enemy – that he would usurp my throne, and even force you to be his wife – and that in the end, we would kill each other.

'So I – I panicked. I did just about the worst possible thing. I could have acknowledged Mordred as my son, or I could have offered to foster him, especially after Lot died and after Mordred's older brothers moved here. Or if I thought this newborn baby was too dangerous to be allowed to live, I could have risked yet another blood feud by sending assassins to kill him specifically, I suppose. But instead, I issued a proclamation that all the children born on May Day must be put on a ship and floated out to sea. I hoped – I don't know. In a way, I hoped that God would take care of the ship and somehow miraculously bring it to a place where all the children could be taken care of. But in another way, I hoped that it would be so far away that Mordred could never find his way back. And as I deserved – and as those children didn't deserve – neither of those happened. The ship sank, most of them were drowned, but Mordred somehow survived and Morgause managed to find him. Maybe that makes him the least lucky of all of them.'

'Is she that bad?'

'Yes,' said Arthur bleakly. 'When I saw her, I thought, "A mother!" – I'd never known my own mother, of course, and my foster-mother, Kay's mother, died when I was seven and Kay was nine. That was the first time I found out that she and Ector weren't my parents, because I was crying, and Kay – it must have been hard on him, because of course he wanted to cry too, but he was the oldest and had to be strong for me – told me I had no right to cry because she wasn't even my mother.'

'What was she like, your foster mother?'

'She was lovely. I remember her telling me, when I was about five, that when I was a baby, Kay used to throw tantrums if she fed me first because he could eat solids and didn't need her milk as much as I did, so she had to cuddle us both on her lap together to feed us at the same time. She didn't know if I was a peasant or a prince, and she didn't care: I was her little boy, as much as Kay was, and that was all that mattered. We missed her terribly, but at least we had each other. And Morgause's older four boys barely had a mother, because she couldn't be bothered with them – my knights who had stayed with her told me that she sometimes showered them with kisses, sometimes hit them, but mostly just ignored them, and that no-one had ever even taught them that it was wrong to kill unicorns – but they had each other, too. But when I saw her, I wasn't thinking about the way her children were obviously afraid of her, and that she probably wasn't a good parent. I just thought, "A mother!" and I wanted her to be the mother of my child. And so now, she is. Poor kid.'

'How old is he now?'

'Seven.'

Guinevere sat up, thinking over what she had heard. Did everyone in this castle want to confess their secrets to her tonight? Would Sir Gawain be here in a minute to tell her about killing a unicorn? She put her arm around Arthur's shoulders.

'Well?' he said at last. 'Do you think now that I'm someone young Lancelot should strive to be worthy to serve? When I'd proved as bad a king as Herod within three years of coming to the throne?'

'I think,' began Guinevere, still trying to get her head around this, 'that if all this had happened decades ago, and we were in our forties, I'd be telling you that you were too young to know any better. But I can't, because you were the same age I am now. You were a grown man who could make his own decisions.'

'Even toddlers know that it's wrong to kill babies. I'm sure Kay was jealous of all the attention I got when I came to the castle, but that didn't stop him being protective of me when I was little. Of course, he was also bossy and infuriating, and we fought like any brothers once I was old enough to grab his toys, but he'd never have harmed me. But no, I wasn't a child at nineteen, and I can't pretend that it wasn't my fault.

'You know,' Arthur went on, 'the average lifespan is thirty-five years, when you count the children who die young, and the old people in their sixties, and all those in between who die in childbirth or in battle or of plague. Merlin says that in the future, when they've discovered things called vaccination and pasteurisation and antibiotics, most people will die of old age, and people will have forgotten that it wasn't always the norm for everyone, and so when they hear that the average age of death for us was thirty-five, they'll imagine that we must have been a fast-ageing race who were grown up at ten, middle-aged at twenty, and old at thirty. Of the children born in Britain the same year as Mordred, maybe three in a thousand were the ones I – murdered. But probably five hundred of those thousand were dead before they were five years old, from some sickness they'd caught from a friend or from drinking dirty water or milk from a sick cow. Maybe instead of inventing the Round Table, I should have asked Merlin to set up a teaching hospital to teach all the physicians in the world about medicine from the future. But that's all just a distraction. It doesn't make what I did any less evil.'

'No.' Guinevere squeezed his hand.

'Do you think I should talk to someone? A priest? Maybe if someone could assign me penance, it could – make this better?'

'I think you probably should talk to a priest. But I thought the point of Christianity is that Jesus has already done penance for your sins. He can bring the souls of those children into Heaven, but I don't see that your wearing a hair shirt or sleeping on the floor could bring them back to life, or make their parents grieve any less.'

'I could sentence myself to death, and then abdicate so that it was legal for someone to put me to death. It wouldn't make their grief any less, but at least they'd have justice, and the knowledge that there wasn't a child-murderer on the throne.'

'You could,' Guinevere admitted. 'But I don't know what would happen to the country if you did. You inherited a kingdom in chaos, and you've only had a few years to start sorting it out.'

'I know.'

'Can you think of any way that you could make it up to Mordred? Or at least try to ensure that he has a fairly happy and safe childhood, and has some chance of reaching adulthood reasonably sane?'

'I don't know.' Arthur considered. 'I should tell Lancelot,' he said. 'If he thinks I'm such a wonderful king, one who is trying to replace the rule of might with the rule of chivalry and justice, he needs to hear what I'm really like.'

'Maybe you should,' Guinevere agreed. 'Not right away, but – he's had a crush on you since the start of puberty. If he's going to decide whether or not he loves you as an adult, he needs to know what you're like, including what you're like at your worst. But don't tell him right now. Give him some time to get to know you and find out what you're like generally. He needs to have some sense of that, before he can know that what you're like at your worst isn't all of who you are, or even the most important part.'