Hilary Simpson was sure daughter Sarah was off work sick until she opened the bathroom door.  Here, Hilary explains how her terrible discovery has left the family in shock. 

I never threw big, flash parties but I always loved celebrating my birthday with my family and a takeaway at home. 

That's all I wanted for my 51st, a special time seeing in another year with my husband Colin, 53, and our children - Sarah, 20 and 22 year-old Will. 

But this year Sarah had to work late so we got together a day early, on April 18.  As usual, Sarah was the life and soul of our little gathering as we drank wine and tucked into fish and chips. 

She worked at a care home and chatted non-stop about the day-trip to the zoo she'd just taken some of the old people on.  But by 9pm she couldn't hold back her yawns - we could tell she was exhausted by her day out. 

"Happy birthday, Mum," she said as she kissed my cheek and headed upstairs. 

When I followed a little while later I heard music blaring from her room, a familiar noise like a comfort blanket - my little girl was home and safe. 

The next morning, I left Sarah to have a lie in before her afternoon shift started while I went to my job as an occupational therapist at the local hospital. 

But when I got home later that day her car was still parked outside - I just assumed one of her friends had given her a lift to work.  I greeted Sarah's pet collie Cleo, who seemed unusually excited, and sat down to open my birthday cards. 

My son Will had also left me some flowers and as I put the vase on the table I noticed a medical book Sarah needed for her training.  I knew she wouldn't have forgotten it so I went upstairs to her room thinking she had called in sick. 

Her bedroom door was open but the bathroom door was locked.  I shouted her name but there was no reply, so I ran to get a screwdriver.  Scrabbling frantically with the handle I finally got the door open and I froze in horror at what I saw. 

My daughter was in the bath, curled on her side.  She looked peaceful, as if she was asleep....but she was underwater. 

Gasping, I reached the icy water.  But the moment I touched her I knew that my girl was dead.  She was cold, stiff and I knew she'd been gone a long time.  I remember screaming before the world faded.  The next thing I knew I was phoning for help.  Minutes later, Colin arrived home to see an ambulance and police cars, and to be told his darling daughter was dead. 

I asked Will to come home and we all sat there, stunned and devastated.  I was too shocked and horrified to even cry. 

Police were everywhere, taking statements, searching Sarah's room.

Will was upset that during all this his sister was laying in the bath upstairs. 

|It seemed so unreal.  Howe could a healthy, happy young woman just die like that? 

Over the following days we went to the funeral home.  Sarah had been dressed in her usual jeans and trainers, her favourite jewellery and had her hair tied back. 

It was awful but at least I could replace that terrible sight of her in the bath with this.  I wanted the last image of my daughter to be how she really looked. 

This time the tears did come and we all sobbed as we sat with Sarah, stroking her hair and holding her hand for the last time. 

We also left letters in her coffin from her friends, telling how much they were all going to miss her. 

The funeral was very difficult but we wanted to give Sarah a fitting send-off. 

Hundreds of people came to the local community centre in Narborough, Leics, afterwards - the place Sarah was planning to hold her 21st birthday party in just six months. 

We should have been there at her party, not her funeral.  Instead the money we had saved up to mark 21 years of her life was being spent commemorating its end.  It all felt so terribly unfair. 

As awful as the funeral was, the next day was worse.   Everyone had left and we were along with our feelings, no distractions or consoling friends and relatives.  We realised this was the beginning of our lives without Sarah. 

We'd been so close, she was like my best friend.  We went on girlie shopping trips together, talked endlessly and laughed over anything. 

That's one of the things I'll miss the most - her bellowing laugh that never failed to make me smile. 

When the post mortem results arrived I was filled with questions.  The cause of death was drowning but how could she have drowned in our home?  It didn't make sense. 

I went back to work straight away.  It really helped to concentrate on other people's problems .  But I had to take things one day at a time because I couldn't - I still can't - look ahead. 

The grief began to feel like an old overcoat that you have to wear all the time.  Some days it feels like lead and hangs heavy on your shoulders.  Sometimes it's a little lighter and you can breathe.  But you know you can never take if off. 

In September, the inquest finally gave use some answers.  The pathologist found that instead of having a big hole for blood to pass through in one of her coronary arteries, Sarah had two little ones that constricted and stopped her heart pumping.  She would have blacked out and slipped under the water. 

We were told that if she'd been sporty, we would have probably lost her as a child on the playing field. 

It was some comfort, knowing that we had enjoyed longer with our child than we might have done.  And we had packed so much into those wonderful 20 years. 

A lot of women can't have children and don't get to experience the mother-daughter relationship that Sarah ande I had, so I know I'm lucky.

Two weeks after the inquest, we went to Sarah's grave on what would have been her 21st birthday.  We found it covered with flowers and balloons with silver keys attached to messages from her friends. 

No one forgot.  And somehow, knowing my daughter and her big heart, I don't think they ever will. 

At the funeral the minister read out some words we'd written, then said: "She would say 'enjoy life and appreciate life and live every day like it was your last.'" 

That sums up everything about Sarah and each time I feel grief threatening to overwhelm me I remember her face and think of those words.  We might not always succeed but we're trying, my darling girl. 

When my birthday comes round again, we'll celebrate the evening before instead and that way I can remember Sarah, happy, smiling and the life and soul of the party. 

The Simpson's have not received payment for this article.  Instead a donation will be made to Cardiac Risk in the Young and their local church. 

What is SADS?

Eight apparently healthy young people die each week in the UK from Sads - Sudden Adult Death Syndrome. 

Cardiac Risk in the Young, together with Philips, has recently launched the Heart Screening Awareness Partnership to increase awareness of, and access to, heart screening for young people. 

Visit www.c-r-y.org.uk/philips.htm for further information and to see footage of CRY's patron, Little Britain star David Walliams.