An Afghanistan veteran and Green Beret who "lived life on the edge and to the full" died after collapsing at the 23-mile mark while running the London Marathon.
Captain David Seath, originally from Cowdenbeath in Fife, was a fire support team commander in 29 Commando Regiment Royal Artillery.
The 31-year-old suffered a suspected cardiac arrest while running the 26.2-mile course on Sunday. He leaves behind his parents Libby and Pete, brother Gary and girlfriend Gaby Schoenberger.
More than £55,000 has since been raised for his chosen charity by his friends and colleagues who are vowing to "complete what he started" - finishing the marathon course for him and continuing to raise cash for Help For Heroes.
Captain James Walker-McClimens of the 7th Parachute Royal Horse Artillery set up the JustGiving page in his memory, which has received thousands of donations so far.
Having served with Capt Seath in the 19th Regiment The Royal Artillery The Highland Gunners in Tidworth, they went on tour together to Afghanistan in 2012, returning at the same time.
"We have stayed in touch ever since, he was at my wedding last year," said Capt Walker-McClimens.
"He was the greatest type of guy you could imagine - everyone loved him. He was funny, outgoing, generous - he was just not a bad guy in any way shape or form."
Capt Walker-McClimens said the news came as a complete shock to all those who knew Capt Seath - and that a "whole group" of friends want to complete the marathon for him.
"In the Army we don't like unfinished business, it was something he wanted to do - he wanted to do the full marathon, so we are going to complete it for him," he said.
"He was raising money for Help For Heroes so we just want to carry on that theme."
He said those who are finishing the course are all fit, but that it is "more fitting" for them to be together when they do it, and will walk the remaining distance instead of running.
Capt Seath's original JustGiving page has also had a flood of donations, with more than £34,000 being pledged for Help For Heroes. He had aimed to raise £250.
His mother Libby Seath said: "David has achieved more in 31 years than most people do in 70.
"He lived his life on the edge and to the full. He was running to raise money for Help For Heroes, a cause which was very important to him."
London Marathon organisers confirmed he collapsed at the 23-mile mark, receiving "immediate medical attention", but that he later died in hospital.
Capt Seath, who was based in Plymouth, completed two masters degrees at the University of Aberdeen before joining the Royal Military Academy Sandhurst in 2009.
Lieutenant Colonel Jon Cresswell, commanding officer of 29 Commando Regiment Royal Artillery, said: "The regiment was devastated to learn of the tragic loss of Captain Dave Seath during 2016's London Marathon.
"Dave was an outstanding commando officer, a natural leader and a true gentleman. He was my assistant adjutant and so I knew him very well.
"He served on operations in Helmand with 19th Regiment Royal Artillery before joining the Commando Gunners and earning his green beret.
"Witty, charming and polished, Dave was a fabulous host and stylish performer. As such, he was the obvious choice to lead the Blue Peter Ten Tors team last year.
"Selected to train the future officers of the Afghan National Army later this year in the rank of major, Dave had a great career ahead of him.
"The thoughts of the regiment are with Gaby and Dave's family and friends at this tragic time. We have lost one of the great characters of our regiment and take strength from the memory of his example and leadership."
The exact cause of death is yet to be established.
To make a donation in Capt Seath's memory, visit: www.justgiving.com/H4HeroDavidSeath.