Tiny Harry weighed just a pound when he was born and was about as long as a pen, but his Dad, Nathan, had also been premature and initially Christina thought that Harry would also pull through.
Instead the family endured a rollercoaster eight months as the little mite continued his battle for survival and he never left hospital. He was five weeks old before they were able to give him his first cuddle.
Harry’s parents Nathan and Beth were overwhelmed with the support and care he received at Southmead.
Beth said: "Through the toughest time in our life the NICU (neonatal intensive care unit) helped to make it bearable and always kept our spirits high.”
Through the tragedy has come enormous good – Nathan has already raised £22,000 for the hospital.
Now the couple have two fabulous children, Freddie, eight, and Gracie, six, but of course they have never forgotten Harry and want to mark his milestone birthday.
Granny Christina, who is not a committed sportswoman, is also joining the challenge and hopes to run from Wellington to Bridgwater.
The team will be calling at Greenslade Taylor Hunt offices in Bridgwater and Burnham-on-Sea along the way before heading back, completing the equivalent of more than two marathons in 24 hours.
The Greenslade Taylor Hunt Charitable Trust has made a donation towards the run. To support the campaign please visit www.justgiving.com/fundraising/nathan-simpson4