She backed up from her 200m heroics to also claim the 50m backstroke.
Junior world champion Atherton is having a strong finish to a breakout year after denying veteran champion Emily Seebohm selection for the 2019 world titles in South Korea where she claimed three medals including 100m backstroke silver.
At the last ISL meet in Budapest in October, she set a world 100m backstroke short-course record of 54.89.
Seebohm, competing for European ISL outfit Energy Standard, was a distant third in Sunday’s 200m backstroke, clocking 2:03.65.
A cashed-up Campbell showed no signs of slowing down in London after her stunning World Cup windfall.
The 27-year-old was clearly still buzzing from claiming more than $400,000 from the just completed World Cup series.
She picked up $200,000 over the seven leg series before being awarded another $A220,000 as the overall women’s World Cup champion.
Campbell is now on track to cash in at the ISL after holding out Swedish champion Sarah Sjostrom by 0.04 of a second to win the 50m freestyle ISL title in London.
Campbell is expected to earn more than $11500 at the London leg.
And if the Roar make the final at Las Vegas from December 20-21 – which features the top two European and US teams – $14,500 goes to each swimmer for the winning outfit.
Other Australian winners on the ISL London leg’s opening night were Emma McKeon (100m butterfly) and Alex Graham (200m freestyle).
Energy Standard (238 points) leads the ISL London leg after the opening night ahead of Roar (224pts), Aqua Centurions (178pts) and Iron (165pts).