Tonelli unofficially led the relay team and was an athletes' spokesperson who fought for the right of Australian Olympians to compete in the face of a government call for a boycott to protest against the Soviet invasion of Afghanistan.

During his stay in America, Tonelli set times that would have placed him among the world's leading swimmers, but he was expelled from the 1978 Commonwealth Games team for breaches of discipline.

His father Lyndon was a blue-collar worker of Dutch origin and his Irish mother Muriel worked in the Queensland Department of Industrial Relations.

The pain of the injury restricted him to swimming backstroke for four months, and his times steadily improved during this period under the guidance of John Rigby at the Valley Pool.

At the final selection event, he came second in both the 100 m and 200 m backstroke behind Olympic gold medallist Brad Cooper to earn his international debut.

[1][12] He claimed a silver in the 4 × 100 m medley relay as Australia were thwarted by Canada despite setting a national record, and was eliminated in the heats of the 200 m butterfly.

However, he was advised to swim conservatively in the first half of the race by Australian coach Terry Gathercole so that his main rivals Matthes and John Naber would not be able to draft behind him in the early stages.

[1] He had swum faster in the second half of the race—something exceedingly rare in top-level swimming and an indication of strategic error—and felt that he had too much unused energy left at the end of the race.

[14] After the World Championships, Tonelli accepted a swimming scholarship from the University of Alabama to train under John Gambril, having rejected offers from Stanford and Harvard.

[1] After enrolling at Alabama, Tonelli's parents paid for him to return home for the 1976 Australian Championships, which were the selection trials for the 1976 Summer Olympics in Montreal, Quebec, Canada.

[16] Tonelli continued in the United States in 1978, recollecting "I really hit my straps", reporting that he had swum world records in time trials at training.

Because he was in the United States, he was allowed to qualify for the 1978 Commonwealth Games in Edmonton, Alberta, Canada by swimming fast times in events in North America.

[21] He returned to Mission Viejo and continued his build-up despite his arm injury, before flying to the Australian training camp in Hawaii,[16] where he was made team captain.

[22] However, his international career appeared to be in disarray when along with teammates Kerry and Joe Dixon, he was expelled from the team for breaking a curfew on the American Independence Day holiday.

In the meantime, Tonelli again won the 100 m backstroke title at the US Nationals in a time two seconds faster than Patching's Commonwealth gold-winning effort.

Tonelli predicted that he could have won eight Commonwealth Games gold medals and possibly set a world record in the 200 m backstroke if he had not been expelled.

[26] In 1979 Tonelli failed to defend his US title in the 100 m backstroke,[12] but managed third in the event at the National Collegiate Athletic Association (NCAA) Championships in his final year of university.

[16] His triumph at the NCAA Championships came amid the backdrop of a teammate's death in a waterskiing accident during a social event with a group of fellow swimmers.

The following year, he repeated the freestyle and butterfly victories in times of 51.80 s and 56.64 s to gain selection for the 1980 Summer Olympics in Moscow; he was also chosen for the 100 m and 200 m backstroke after finishing second to Kerry.

However, another obstacle arose with the Soviet invasion of Afghanistan, which resulted in a boycott of the Games by a large part of the Western world, led by the United States.

[28] Tonelli's anti-authoritarian and individualistic style manifested itself during media appearances,[31] including a news interview in which he debated with Reverend Lance Shilton, who had referred to the athletes as traitors.

Unaware that the camera was broadcasting images of him, Tonelli responded by rolling his eyes and twirling his finger, a gaffe that was shown on national television.

However, Tonelli split 1 m 53.47 s, the fifth slowest time among the 32 swimmers, resulting in Australia falling back to seventh place by the end of his leg.

Australia was regarded as a chance of a medal, but were not seen as the main threats,[38] with Sweden, Great Britain and the Soviet Union the most heavily fancied teams.

The British boasted Duncan Goodhew, the breaststroke gold medallist, while Sweden's butterflyer and backstroker had won their respective events and their freestyle swimmer would come second in the 100 m.[38] On paper, Australia's team paled in comparison.

[29][41] Adding to the pressure was the fact that Australia won no gold medals at the 1976 Olympics in any sport, so the public were still awaiting their first victory since the 1972 Games in Munich.

The Soviet freestyler pulled level at the 25 m mark before Brooks sprinted away again to seal an Australian victory by 0.22 s. He had finished his leg in 49.86 s as he had vowed to his teammates.

[46] The quartet did not receive the customary congratulations from Fraser, who initially resisted complaints the next day from the media and government members at his failure to applaud the Australian victory.

[46] Fraser had ordered the Australian diplomatic mission to shun the Olympians,[48] so the embassy staff had to pass the envelopes containing the message through the Olympic Village fence.

[50] One policy that he proposed was the creation of an athletes' appeal tribunal similar to the Court of Arbitration for Sport so that "officials are now held accountable for their actions".