Their reasoning was that he would have neither the strength nor the stamina to compete with the 50 other racers, all of whom were less than half his age.
Nevertheless, having ridden 600 miles to get to the starting line, Håkansson was there on race day in the saddle of his roadster complete with mudguards, a headlamp, front basket and panniers. He wore a homemade bib with the number 0 on it.
Due to the volume of racers, Håkansson crossed the starting line about 20 seconds after the race had started, but five days, five hours and 1,000 miles later, he crossed the finish line first – more than a day ahead of the next rider.
Håkansson had not been bound to one rule that the other 'official' participants were obliged to follow. As part of race regulations, competitors were expected to meet and stop at a checkpoint at the end of the day to recharge and restart the next morning.
Instead, Håkansson took just an hour's rest before setting off again in the middle of the night. This allowed him to make up for the 10 miles he was behind after 300 miles and put a 20-mile gap between himself and the rest of the pack.
After three days and only five hours' sleep, Gustaf was leading the field by more than 120 miles. At one point the police tried to persuade him to stop for a medical examination, but he only laughed and pedalled on.
Eventually, with only 800 yards or so to go, Stålfarfar or "Steel Grandpa"; as he became known in the villages he'd passed through, came to an abrupt halt. But it wasn't sheer exhaustion that had stopped him – the old man's bicycle had suffered its first and only flat tyre.
Unperturbed, Gustaf dismounted and set towards the finish line where, with only a few yards to go, he remounted to cross the line at 2:15pm on July 7, 1951.
Despite the albeit unofficial victory, a subsequent audience with the king of Sweden, and generally being showered in fame and honour, Gustaf's greatest satisfaction came from proving wrong the doctors who had thought he was better suited in a rocking chair than he was in a saddle.
The Steel Grandpa continued to ride bicycles until his death in 1987 at the age of 102 and if that isn't a testament to the health benefits of riding a bike, then I don't know what is.