Tom Pidcock, the Olympic champion, secured a memorable gold medal in the world championships in the Tweed Valley, dominating the final laps of the cross-country Olympic discipline. Pidcock, who became the first British man to win the title, held off a late chase from New Zealand’s Sam Gaze, after moving into the lead at the start of the last two laps.

“It’s a big relief,” Pidcock said of his victory. “It’s been a long week building up to this. In front of the home crowd, it’s pretty special. The last few laps were so stressful. My gears were not working well. They were jumping, up every climb. Gaze was coming and I thought it could all go in the bin at any moment.”

Related: ‘He rode into me’: Tom Pidcock accused of causing crash on way to world bronze

The race started dramatically when Mathieu van der Poel came to grief on a right-hand downhill corner just before the end of the start loop, tumbling on to the same right side that he had injured when crashing during his world road race win in Glasgow a week earlier. The Dutch rider abandoned the race immediately, forgoing hopes of becoming the first male rider to hold world cyclo-cross, road and mountain bike titles in one season.

But the sense that the mountain-biking community had been forced into kowtowing to Pidcock, Van der Poel and the former Tour de France green jersey winner Peter Sagan persisted, after more than 20 elite men and women racers, including the bronze medallist, Nino Schurter, had signed a letter protesting against what they saw as preferential treatment.

“We are really not happy [with] how the UCI is treating our discipline by changing rules regarding start position one day before the race,” the letter said. “The point is not whether the rule being applied is fair, unfair or appropriate. What matters is the manner and timing in which the UCI applied and enforced this rule. And the consequences that follow for individual riders and teams with quota positions for the Olympic Games.”

In a convoluted interpretation of the UCI’s rules, the Tour de France stars were in effect bumped up the start grid for the men’s cross-country Olympic race. The UCI sports director, Peter Van den Abeele, said: “I wouldn’t call it favouritism. It’s about the added value of the sport. A mountain bike race with Pidcock or Van der Poel is of a different calibre than a mountain bike race without those two.”

After the race, Pidcock described the decision as “bullshit”, adding: “It’s pretty outrageous. This week they changed the rule. You can’t do that.”

In the women’s cross-country Olympic race, Pauline Ferrand-Prévot took her fifth world title, with Britain’s Evie Richards finishing sixth.

In the men’s under-23 road race, the folly of taking the world’s best riders through so many tight corners and over pedestrianised surfaces in the Glasgow rain was laid bare, as 26 separate crashes turned the race into a farce. The peloton was soon diminished as a group of eight, including Britain’s Jack Rootkin-Gray, raced into the final kilometres.

Rootkin-Gray fought hard to stay in contention, but finished fourth in the sprint, behind the race winner, Axel Laurance of France. “It was brutal, to be fair,” Rootkin-Gray said. “I just didn’t have quite enough to do what I’d hoped to do.”

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In the para cycling disciplines, Dame Sarah Storey took yet another road title, her 18th, in the women’s C5 road race. “It feels amazing,” Storey said. “I can’t ever take it for granted that’s how a race will go. It does seem there’s no stopping me, but it’s because there’s a huge amount of work that goes on behind.”

Elsewhere, on a busy day of para cycling racing, Fran Brown took gold in the women’s C1 road race, Will Bjergfelt took gold in the MC5 road race, as did Fin Graham in the MC3 road race. Archie Atkinson claimed a bronze in the MC4 road race and Ben Watson did likewise in the MC3 road race, while Sophie Unwin and Jenny Holl also won bronze medals in the women’s B road race.