The first time I met her, she was wearing blue. It was at a 'Fauna and Flora' convention in Sweden, and she was swaying among the tables to a tune only she could hear, arms entwining above her head. 'Is she ok?' I murmured to Archie Mutton, my research partner of many years. He looked at her and grinned. 'That's just Luna Lovegood,' he said. 'She's a bit loopy, that one…comes here every year looking for Crumple-Horned Snorgys or something like that.'

I laughed along with him, but deep down, I was envious of a person who was so ready to believe, who didn't need proof of existence but rather proof of inexistence.

The second time I saw Luna Lovegood was at a memorial for the fallen, five years after the Battle. Most of the wizarding world had turned out, as it had been rumoured Harry Potter himself would be speaking (as it turned out, he didn't – his friend Neville Longbottom had instead.) To my surprise, Luna was sitting up the front with those we heard so much about – the Weasleys, the Granger girl, Potter himself. 'Was she there?' I asked Archie. Archie shrugged.

'I think she was a member of Dumbledores army…and her father runs the Quibbler, you know, it was the only pro-Potter publication for months back then.'

I couldn't take my eyes off her – but then again, neither could a great deal of the congregation; she was wearing possibly the most fluorescent orange robes I'd ever seen.

The first time I spoke to Luna, she was wearing a purple cloak. It was in Diagon Alley, outside Flourish and Blotts. I'd just come from signing over a consignment of my fathers books, and as I hurried out the door, I'd bowled into her, knocking her over.

'Oh Merlin – I'm sorry!' I'd exclaimed, taking her elbow and hauling her to her feet.

'Don't worry,' she said softly. 'I expect the Wrackspurts were floating in front of your eyes for a minute – they like to live in hair like yours, all long and messy.'

I blinked. 'Um…'

'Not that I don't like your hair,' she continued airily. 'It's quite attractive, you know.' She smiled at me, and my stomach jumped.

'Can I get you a drink in the Leaky Cauldron?' I found myself asking.

'Of course,' she said. 'But we'll have to be careful of all the mistletoe they've put up – it's bound to be infested with Nargles.'

I kissed Luna in a green field. We'd been on a picnic, and then gone searching for grass-pixies, a miniature speckled variety. Luna had flung herself down on the grass, pinkcheeked and puffed. 'It smells sweet, doesn't it?' she'd said, crushing some blades between her fingers. I'd grinned, and wrapped a hand in her long, blonde hair and kissed her. A few moments later when we were sitting nose-to-nose, staring each other in the eye, she'd smiled back at me and said in that straight-forward way of hers that I adored 'That was nice. Should we do it again?' I'd realised at that moment that I loved her.

I proposed to Luna in a sea of pink flowers. We walked through the front door after an afternoon of writing up pages and pages of my fathers notes on magical beasts, and the charm I'd set that morning went off, and the flowers rained down from the roof, burst out of the walls, sprouted up from the floor. Luna began to laugh and, holding her arms out, twirled round in circles like a child, catching at the flowers with her hands. 'Luna,' I'd shouted over the music that had begun to play (I'd been over-enthusiastic with the spell and it was louder than I'd anticipated), 'would you like to marry me?'

She'd continued twirling for a moment, and I wondered if she'd heard. I was about to ask again, when she tucked on of the flowers behind her ear, skipped over to me and shouted 'Yes!' back. And then I was twirling with her amongst the flowers, laughing with her, happier than I'd ever been in my life.

We had a yellow wedding. 'Yellow is the happiest colour,' Luna told me firmly. And so she'd worn butter-cup yellow dress robes, and I'd worn yellow robes too (ignoring Archies sniggers – he flatly refused to wear yellow robes and so the best man wore white), and we'd had yellow flowers and yellow food (custard and bananas and things like that) and then, during our first dance as husband and wife, yellow flowers had rained from the ceiling just like when I proposed and we'd laughed and twirled again.

We'd painted the room for our children blue. Lycan and Lysander, born three minutes apart, born after five years of longing for a child. We sat by the side of the cradle, clutching each others hands as we'd stared at these perfect, beautiful children – our children, mine and Lunas. She'd held her breath suddenly as one yawned, and moved slightly, the curled his fist around his brothers arm. They already had soft blonde hair like their mothers curling on their gentle heads. And however happy I'd been before, I was most joyous at this moment, staring at these beloved children, Luna clasped tightly to my side.

I met a young girl, and she gave me the rainbow.