Think back to the quick goodbye hug you and your loved one had this morning.  Now imagine it was your last.  That's the image James Brown, 31, plays over in his mind every day.  

The date was the 2nd of July last year and it was a beautiful sunny day.  My wife Katrina and I were in London for the British 10K race.  We'd been married two years and it had been our New Year's resolution to enter more races - we'd been training together for months.  There was a wonderful atmosphere as we made our way to Hyde Park Corner for the start, and like me, Katrina was excited to be running.  She always said: "there's nowhere I'd rather be than London when the sun is shining". 

'It was a special moment - but our relationship was full of them.  We met in 1996 in Salamanca, Spain, where we were both studying as part of our degrees.  A mutual friend introduced us one balmy evening in an Irish bar by Plaza Mayor.  Katrina's long curly hair and amazing smile blew me away instantly, but it was her air of confidence and the way she drew me in when she spoke that captivated me.  After that night we spent every second together and although I was supposed to be studying, all I could think about was Katrina. 

'Back in England, I had a year left at Southampton while Katrina was in Aberystwyth, but we still saw each other as often as we could.  Although we were both only 20, I knew I wanted us to be together for a long time, so I was delighted when Katrina moved down to London and we were able to spend more time together.' 

'I always knew I'd ask Katrina to marry me, but it took me another five years to get round to it.  We were on holiday in Spain and I'd arranged a trip in a hot air balloon, which was a rash decision on my part because I'm absolutely terrified of heights.  I spent most of the time gripping the basket nervously, but eventually, as we floated out across the country in which we'd first met, I managed to prise my white knuckles off the sides and get down on one knee.  There was a pause as tears rolled down Katrina's face, then she whispered the only word I needed to hear, "Yes." 

'Katrina spent ages planning our wedding.  She was good at organising things, so it's no wonder the big day was the happiest of my life.  Katrina looked so stunning as she walked down the aisle, she literally took my breath away.  I felt like the luckiest man alive. 

'Married life was even better.  As a couple we just fitted together perfectly.  Katrina was always so happy and upbeat and I loved coming home to her beautiful glowing face at night.  She was always so thoughtful, too, like the party she organised for my 30th birthday last year.  She invited all our friends and even bought a football-shaped cake for me.  I still have a lovely photo of us looking so happy together on that night.' 

'So a week later there we were on the start line at Hyde Park Corner.  We planned to begin the race together, but knew with 30,000 people taking part we'd probably lose each other pretty quickly, so arranged to meet just past the finish line.  We had a good luck hug, plugged in our iPods and set off.  Sure enough within a few minutes of the gun going off we'd lost sight of each other. 

'With my favourite tracks blaring, I pounded my way round the course on a total high.  When I crossed the line 48 minutes later I couldn't wait to share the moment with  Katrina.  I was looking forward to a well-deserved drink with her, but after ten minutes of trying to spot her, she was nowhere to be seen. 

'Suddenly the crowds parted as two paramedics ran past, 

I figured some poor guy must have collapsed, but still found myself following them - and that was when I caught sight of a body on the ground and Katrina's familiar grey shorts and her Asics trainers.  My whole body went into shock as I frantically fought my way through the crowd.  I was desperate to be by Katrina's side, but the paramedics ordered me back to give them space to work.  I called out to her to let her known I was there, and in the hope of walking her from this madness, but there was nothing. 

'I stood dumbstruck as my worst nightmare played out before me.  Howe could this be happening?  Katrina was an incredibly fit, healthy woman - there was no reason anything should be wrong with her.  She swam and did yoga every week, and we both had really healthy diets. 

'Within minutes an ambulance arrived and I was ushered into a police van and driven to hospital.  I still didn't have a clue what was going on and I kept repeating over and over "I can't believe this is happening."  When we arrived at the hospital I borrowed a mobile and called our families. 

I couldn't tell them much apart from that Katrina had collapsed after the race and I was waiting for news - I was so frightened.  It felt like hours as I stared at the walls of a private room in A&E, praying for good news. 

'My brother and his wife were the first to arrive at the hospital.  Shortly after they got there a doctor came into the waiting room and I knew from the expression on his face it was bad news.  "I'm sorry," he whispered.  "Your wife is dead."  My mind refused to believe it.  I just went numb and lifeless - it felt so unreal.  Telling Katrina's mum and sisters was the most difficult thing I've ever done. 

After that the doctors gave me time alone to say goodbye to my gorgeous Katrina.  I still can't talk about that moment. 

'Katrina's family rushed down from the Midlands and we spent the rest of the day comforting each other in shock and disbelief.  That night my parents asked me to stay at their house but I wanted to go home to feel close to Katrina.  Arriving home where everything seemed so normal was tough, but two of Katrina's sisters stayed with me, which helped keep us all strong.' 

'The next few days passed in a blur of funeral arrangements, cards and flowers.  A week later I was standing in the same church Katrina and I had been married in two years before, only this time instead of gazing at my beautiful wife in a state of pure happiness, I was the most devastated person alive.  The church was crammed full of family and friends all in the same state of shock as me.  I managed to bet up and speak about how thankful and proud I was to have known Katrina and to have had her in my life. 

'It was only weeks later that we found out how she'd died.  Katrina had a slight abnormality with one of her heart valves.  Perhaps if she'd had an ECG it would have shown up.  Andy maybe if we hadn't run that day, she'd still be here now...but I try not to torture myself what what 'ifs. 

'I*it's been just over a year now since Katrina died.  I still live in the house we shared - it helps me to feel close to her - and do my best to keep it clean and tidy the way we always kept it.  I still go running, but now I'm on my own.  The first time without Katrina was emotional - all sorts of memories came flooding back - but it also gave me time to get away from it all and now I use it as a chance to raise money for Cardiac Risk in the Young ((CRY), a charity that raises awareness of heart problems in young people, as well funding medical research into sudden death, donating cardiac equipment to hospitals and supporting a national heart-screening programme.  On a personal level, the charity has provided an amazing support.  With the help of family and friends I've managed to raise around £85,000 for them and now whenever I'm running, happier memories of Katrina fill my mind - including that last hug she gave me before the race. 

'There's so much I miss about my wife.  So much.  But it's not being able to hold her in my arms that is the hardest of all.  I guess I'm still taking it one step at a time.' 

To make donations to CRY through James' site for Katrina visit justgiving.com/mykh