Halep's victory certainly did not come easily, the world number one forced to come from a set and a break down to overcome Kaia Kanepi, the powerful Estonian who beat her in the first round of last year's US Open.

Kanepi's lack of consistency ultimately proved decisive as Halep triumphed 6-7 (2-7) 6-4 6-2 to claim her first win since August, having missed the latter stages of the 2018 season due to a back injury.

While Halep was pushed by her opponent, the likes of Serena Williams, Naomi Osaka, Elina Svitolina and Karolina Pliskova all progressed in routine fashion.

Daria Kasatkina, Mihaela Buzarnescu and Dominika Cibulkova were the only seeds to bow out on Tuesday, suffering respective defeats to Timea Bacsinszky, Venus Williams and Zhang Shuai.

Two-time champion Victoria Azarenka was beaten by Laura Siegemund and cut an emotional figure in her post-match news conference.