Most people celebrate their 40th birthday with a slap-up meal or a surprise party.

Gael Monfils, the maverick Frenchman who always knows how to have fun on the court, marked his milestone by winning a Grand Slam match at the US Open.

Playing in the final major of his career, Monfils ensured he had a unforgettable night with a 2-6 6-1 6-2 6-0 victory over Paraguayan opponent Adolfo Daniel Vallejo.

The former world number six is the oldest man to win a US Open main-draw match since Jimmy Connors – who also won on his 40th birthday in 1992.

The New York crowd made the occasion even more memorable for Monfils by bursting into an impromptu rendition of ‘Happy Birthday’ during his post-victory interview.

“To play on my 40th birthday is very special,” said the 2016 US Open semi-finalist, who announced last year he will retire at the end of this season.

“The atmosphere [in New York] is always electric – I feel great here. I always try to play great tennis and put on a great show.”

Addressing the thousands of fans who created a celebratory atmosphere on Louis Armstrong Stadium, he added: “You guys rock – let’s keep it up for the second round.”