Preston had a breakthrough result as an 18 year-old when he won the 800m at the Porritt Classic in New Zealand in February 2016, beating New Zealand champions
Brad Mathas and
Hamish Carson, and breaking his personal best by three seconds. In March 2022, Preston won his second New Zealand national title over 800 metres. In July 2022, he became the third fastest 800m New Zealand athlete in history, behind
Peter Snell and
John Walker, when he ran 1:45.30 in Germany. In February 2023, Preston won the 800m at the World Athletics Continental Tour Gold Meet in
Melbourne in a world-leading time. At the 2024
New Zealand Track & Field Championships Preston ran 1:44.87 to become the second fastest New Zealander ever over the distance behind
Peter Snell and ahead of
John Walker. On 25 May of that year, in
Pfungstadt, Germany, Preston broke Snell's 62-year-old
New Zealand national record in the 800m, the oldest athletics record in New Zealand and one of the oldest in the world. He competed in the 800 metres at the
2024 Summer Olympics in Paris in August 2024. Preston qualified for the final of the 800 metres at the 2026 New Zealand Athletics Championships in Auckland, running 1:53.53, before winning for final the following day in 1:46.58.{{Cite web | url= https://worldathletics.org/competition/calendar-results/results/7235518?eventId=10229514&gender=W == References ==