Maskill’s success came moments after Ellard took silver in the men’s race.
The 18-year-old from Suffolk led at halfway with Alexander Hillhouse down in fourth, but the 20-year-old Dane came through in the second part of the race in a new Paralympic record of 54.61 seconds, with the Briton clocking 54.86.
“I didn’t think I would be happy with silver but I am,” said Ellard. “It gives me more confidence for my 200m freestyle, which is my main event.”
Ellard was being interviewed by the media as Maskill won her gold and he was thrilled to see his team-mate achieve glory.
“It’s big for the team and a huge personal best for Poppy as well,” he added.
“I know she wants to try to get the world record in the 100m backstroke later in the programme, but this is a big bonus for her.”