Going head-to-head with sister Venus for the 30th time brought out the best in Serena Williams as she hit top form at the US Open.

Just before the match, Serena shared a video on Instagram from exactly a year ago when she was in labour preparing to give birth to daughter Olympia.

There will be further tests to come that will show whether she is totally back to her best, but there was little to fault as she raced to a 6-1 6-2 victory in just an hour and 11 minutes, equalling the most one-sided match in their long history.

The sisters shared an embrace at the net before a muted wave to the crowd from Serena, who will next face Estonia’s Kaia Kanepi.

‘It’s not easy,’ said the 36-year-old. ‘She’s my best friend, she means the world to me and she’s so supportive of my career and I’m extremely supportive of her career. Every time she loses I feel like I lose. I love her with all my heart and she’s the only reason I’m still out here. I owe everything to her.’