An average audience of 3.5 million viewers watched Diana: In Her Own Words on Channel 4 last night.
The feature length documentary, which broadcast previously unseen recordings of the late Princess, proved controversial but pulled in big viewing figures.
A peak audience of 4.1 million watched the show, giving Channel 4 one of its biggest audiences in years.
Over on BBC One at the same time, the World Athletics Championships averaged just over 5 million for its latest day of coverage from the London Stadium at the Queen Elizabeth Olympic Park, peaking with an audience of 7.3 million.
The sports overran slightly, pushing back the series finale of Poldark which ended with 4.9 million viewers.
Over on ITV The Chase's latest Celebrity Special averaged 2.7 million viewers before Harry Potter and the Half Blood Prince had 3 million.
On Channel 5, Celebrity Big Brother rebounded from Saturday's low to 1.1 million viewers, down 400,000 on last year's first Sunday show but level with 2015.
Following CBB's latest house highlights, The Last Days of Patrick Swayze averaged 1.3 million.