The race director of one of Britain's most arduous runs has died while on a hill run in Aberdeenshire.

Dario Melaragni, 46, who was known to friends as the "Race Daddy" of the West Highland Way Race, is understood to have collapsed near the 3790ft summit of Lochnagar on Saturday.

The personal trainer from Blackford, Perthshire, who has organised the race for the past nine years, had been out on a walk and jog with a group of friends. They tried in vain to resuscitate him.

It is believed he may have died of a heart attack.

The group aimed to walk roughly 20 miles across Lochnagar and four other Munros, climbing up to 6000ft en route.

The West Highland Way Race, which is in its 18th year, is a 96-mile endurance event from Milngavie to Fort William that takes even hardened hill walkers several days to complete.

Gary Milne, who was with Mr Melaragni on the expedition, described it as a "sick twist of fate" and added: "We, his friends, fought for almost two-and-a-half hours to save his life but unfortunately he could not hold on.

"Dario was not a tall man in stature, however he had a heart of gold and an infectious personality that made him a giant. He will leave a massive hole in the lives of many. It is a small comfort to know Dario died doing what he loves in the company of friends. I will miss him greatly."

Jonathan Outterson, Mr Melaragni's brother-in-law, said the events of the weekend had been "indescribable" for the family and especially his wife, Gillian.

"I would just like to convey my thanks to those who were with Dario in the hills for their efforts - I know how awful it must have been for you all," he said.

When organising the "jaunt" Mr Melaragni said in messages to fellow runners that it was "all on reasonable tracks (it appears)".

Many moving online tributes have been paid from runners and walkers to the civil servant who formed his own athletics club, Harlequins, and became a personal trainer.

John Kynaston, pastor of Hopehall Evangelical Church in Paisley and a helper with the race, said: "I have been involved with the race only for the last three years but I'm so glad I have, as it has given me the opportunity to meet and get to know Dario. I don't think I really appreciated just how much time and effort he put into the race.

"We had a good chat at the barbecue after the race and he was full of plans to make the race even bigger and better. There is no doubt that it won't be quite the same without him but I have a feeling that his leadership and example will guide the race for many years to come.

"I really loved the way he made the race so special for everyone. He made it a very competitive race at the top end but also made everyone who took part feel that they were just as important as the winner."

Friends said such was his love of the sport, Mr Melaragni would often run from his home in Blackford to his work at the tax office in Stirling.

The West Highland Way Race was first conceived in 1985 by Bobby Shields and Duncan Watson, two Scottish runners who decided to race each other from Milngavie to Fort William on a popular but uncompleted 85-mile West Highland Way route. Over the next five years, the June event gathered momentum, drawing a select group of like-minded enthusiasts.

In 1991, following the completion of the current 96-mile trail, the official race was inaugurated.

Starting from Milngavie train station, participants must run, walk, plod and shuffle between eight checkpoints along a rocky and hilly off-road route. The overall ascent is 14,760ft - more than three times the height of Ben Nevis - with several serious climbs including 1200ft Conic Hill, the 1850ft Devil's Staircase and a long haul out of Kinlochleven in the final 14 miles of the race.

While in the early 1990s an average of only 25 people signed up to run, it now attracts more than 100.