Paul Casey four shots off the lead after opening round 67 in Tokyo

British golfer Paul Casey was proud to call himself an Olympian after a fruitful four-under-par 67 in the opening round of the men’s event at Kasumigaseki Country Club.

Casey finished the first day three shots ahead of compatriot Tommy Fleetwood, with Austria’s Sepp Straka sitting atop the leaderboard overnight after a blemish-free 63 featuring eight birdies.

For Casey, though, merely stepping on to the course at Kawagoe in Saitama, about 20 miles away from downtown Tokyo, was a fulfilment in itself.

“I just felt really proud, it was the coolest thing I’ve ever done in golf, there was not an ounce of nerves, just 100 percent excitement,” said Casey, who recorded birdies at the fifth, seventh, eighth and 14th holes in his bogey-free round.

“I’ve thought about this for so long because you can’t count yourself as an Olympian until you’ve started your competition. It was brilliant but then I got down to business.

“This might be the only chance I get to win an Olympic gold, there will be other chances for majors.”

Straka, ranked 161 in the world, is just a single stroke ahead of Thailand’s Jazz Janewattananond while Belgium’s Thomas Pieters and Mexico’s Carlos Ortiz are a further shot behind in the 60-man field.

Lightning in the area led to a temporary halt to proceedings on Thursday, after which Fleetwood completed a round which fluctuated between good and bad, ending on the latter with a double bogey six on the final hole.

“I’m pretty deflated about the way I finished, that leaves a bit of a sour taste,” said Fleetwood.

Shane Lowry finished alongside Fleetwood on 70 while fellow Irishman Rory McIlroy currently sits on two under.

When asked what it would mean to be crowned Olympic champion, McIlroy said: “I don’t know. I never dreamed of that.

“I dreamed of Claret Jugs and green jackets. I never dreamed of winning the Olympics, so I don’t know what it would mean until you’ve actually got one.

“It’s a hard one to put into words. If it wasn’t an option for you growing up and dreaming about it…maybe I could articulate it a little better if I was in possession of one.”

Justin Rose won the inaugural event at Rio 2016, so Casey admitted the pressure is on to keep the gold in British hands.

“I guess we have a lot to try to live up to, we are defending gold technically, Team GB,” Casey said.

“It’s interesting my priority has now shifted from ‘I just want to be an Olympian, go to the Olympics’ to now ‘I am here I am taking it very, very seriously’.”