Mickelson plays down LIV switch: Let it go dude, I couldn't be happier

Briton Poulter was booed on the first tee before shooting a three-under-par 69 and Mickelson was unfazed by his decision not to attend the pre-tournament champions dinner.

"The R&A contacted me a couple weeks before and said, look, we don't think it's a great idea you go, but if you want to, you can," the American six-times major champion said.

"I just didn't want to make a big deal about it, so I said fine. We both kind of agreed that it would be best if I didn't."

The 52-year-old Mickelson, who started with a level-par 72 at St Andrews, was delighted to be at the home of golf.

"I love being here. Everybody here loves golf, and we find this place to be very spiritual," he said. "It's just a special place."

Mickelson said he was very comfortable with his decision to join the LIV series.

"I couldn't be more excited and ecstatic with where I'm at," he said. "I love the events. I get to have competitive golf in my life on a scale that is fun, exciting, different, and lets me play and compete but still do the things outside that I want to do."

He did bristle when asked again about the champions dinner.

"Let it go, dude. Let it go," he said. "That's three times you've asked the same question. I don't know what to tell you. I couldn't be happier."

Poulter, revered in European golf for his inspirational Ryder Cup performances, was booed by a few spectators, although the Englishman appeared not to notice.

"I actually thought I had a great reception on the first tee, to be honest," he said. "All I heard was clapping."

Poulter reacted with indignation to suggestions he was heckled around the course.

"Oh, my gosh, I have heard not one heckle. In three weeks, I've heard nothing," he said. "You lot can write whatever you like about being heckled and booing."

Poulter said his relationship with other players had not been affected by his decision to join the LIV breakaway.

"We might have a difference of opinion, but they're my friends," he said. "You play golf with these guys for 20-plus years or 10, 15 years, you've been part of many teams with them. We're still friends, whatever the landscape is and wherever you're playing golf."

Poulter will not allow himself to be distracted as he bids to win his first major title.

"I'm here to play golf. This could probably be my last Open Championship at St Andrews. So I'm trying to enjoy it despite the questioning," he said.

"I shot three under. I was quite happy. I was nice and relaxed."