The 'cheeky' 13-year-old, who was a member of his local swimming squad, died of the killer brain infection in hospital on Sunday evening.
Graham Irvine, senior coach of Fins Swimming Club in Kirkcaldy, Fife, said he was struggling to take the tragedy in.
"Gregor had been at the club as long as I can remember and we were looking to develop him into an athlete as he moved through adolescence," he told his local paper.
"He will be missed greatly by his peers within the squad as they spend a considerable time with each other training and become more like family than friends.
"His confidence and cheeky ways will be how I remember him most as we come together as a club to try and come to terms with the pain and unfairness of his passing."
Gregor's older sister, Rachel, took to Twitter to share the news and express her distress.
Derek Allan, Rector of Kirkcaldy High School where Gregor was a student, said today that both pupils and staff were shocked and saddened by his death.
"Our thoughts are with his family and his many friends during this very difficult time," he said.
"Gregor was a popular pupil, well known and liked by staff and pupils. He will be a huge loss to us all.
"We have also set aside some quiet space in the school for pupils and staff, who are being comforted by our own staff and a Fife Council support team."
The school is liaising with Fife's public health team and all pupils have been given leaflets highlighting the symptoms of meningitis.
However, it is thought to be very unlikely that any other pupils will contract the illness. Gregor's devastated parents, Jenny and George Smith, are now planning his funeral.
And his friends at Kirkcaldy High School are organising a sponsored walk to raise money for research into meningitis.
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