For every day of the four short years of Megan's life, we knew she was almost certainly going to die. Like Ivan Cameron, she was diagnosed with epilepsy and cerebral palsy soon after birth; like him, she was severely handicapped - in a wheelchair, having lots of fits, needing constant care. We were warned that there was a high risk she wouldn't survive for long. Yet, despite that, nothing could prepare us for the crushing experience of losing her. However much the Camerons knew this might happen, they will be reeling from the shock. Human imagination isn't that good. We don't have the capacity to anticipate the feelings that come about when our child dies.
When you are caring for a child such as Megan or Ivan, life is fuller and faster than you would have thought possible. Megan needed 24-hour care, just as Ivan did, and it's desperately intensive. Megan had to be tube-fed, and she needed to be suctioned so she could breathe properly. She had to have physiotherapy daily to keep her chest clear, and her position had to be changed regularly. Add to that the bathing, dressing, changing and all the ordinary things you do for a child - doing their teeth and hair, playing with them - and there was never a moment when you weren't busy.
But the rewards were tremendous - Megan was a star. She was never able to speak, but she could certainly communicate. She had a huge smile and told us with her eyes what she wanted - she'd point to things, and if she didn't like something she'd poke her bottom lip out. She was very intelligent: she could get her needs across and was able to make choices. She had likes and dislikes - she adored the Tweenies and loved pink. Others might not have been able to tell what she wanted, but we always knew. My other children - Tom, now 23, Amy, 21, and Isy, 19 - loved Megan so much. She laughed like a drain, and could certainly encourage them to be naughty. They had a lot of fun together.
Megan's death was also very sudden. She had been a bit under the weather, and she died in her sleep. She slept in our room, and I remember waking up around 2.30am and thinking, I can't hear Megan moving around. I put on the lights, and tried to resuscitate her, but she was gone. It was the end I would have chosen for her - she was in her own bed and there had been no struggle - but that didn't make it any easier.
There is no formula for survival - you just have to go on however you can. You take one day at a time, and you have to remember to be really, really kind to yourself and to the other people closest to you. My children were devastated at Megan's loss. Tom was only 15, but he wrote and delivered the eulogy at her funeral and the girls chose a poem.
It is the other children who keep you going. They were the reason I got up in the morning after Megan's death. We had to establish the normal ebb and flow of daily life for their sake, and that's how I started to rebuild our lives.
Losing a child, as well as looking after a child like Megan, does take its toll on a relationship. It's hard enough to be married, and it's a lot harder if you're looking after a disabled child at the same time. Megan's father and I split up a couple of years after her death.
Just before she died we had opened Megan Baker House near our home in Leominster, Herefordshire. It provides a therapy called conductive education for children such as Megan, and around 200 children a week currently come here. At first I wasn't sure I'd be able to carry on with it, but I found I could - and it has given me new reasons for carrying on with my life.
Megan will never be forgotten by any of those who knew her. I know her story sounds sad, but it isn't sad because she was a wonderful little girl who lived a life full of laughter and joy, and she brought laughter and joy to others.
Her legacy is in the fabric of my life and in all the lives that are touched by Megan House. Finding a project that connects me to Megan brought me a lot of healing, and my greatest wish for David and Samantha Cameron is that they too will find a way to weave Ivan's memory into their lives and the lives of their other children, so that part of Ivan goes on living with them into the future.