Matt Kuchar was delighted that his "challenging" experience at the Scottish Open proved valuable as he started his bid for glory at Royal Birkdale in style.
The American, whose Open debut came in 1998 on the same course, shot a blemish-free 65 to join Jordan Spieth and U.S. Open champion Brooks Koepka at the summit of the leaderboard.
He went out in 29 and saw a birdie putt skirt the cup on 17, denying the 39-year-old the outright lead at a track he conceded to having forgotten "just how good it was".
Though the weather - which is forecast to take a turn for the worse - was generally favourable throughout Kuchar's round, the winds did sometimes pick up and, having played in horrendous conditions at Dundonald last week, he was glad to have put himself through that gruelling preparation.
Bogey-free. Co-leader-- The European Tour (@EuropeanTour) July 20, 2017
Matt Kuchar's cards his best ever Major round (152 rounds) pic.twitter.com/PNbNviEHxR
"[I] was really happy with my performance last week at the Scottish Open," he said, having finished joint-fourth there.
"We had a couple of awfully challenging days there at the Scottish Open. At one point on the 12th hole Saturday I had 129 yards to the pin and hit a six-iron in and thought to myself, 'I am glad I'm over here, glad I'm doing this'.
"It was extremely difficult conditions, but this is not something I can ever remember doing in the States. And just getting a feel for playing the different shots that you are required to play over here.
"So after last week's good performance I thought it's a perfect tune-up for coming into this week. I think everybody thinks Royal Birkdale is just a fantastic test of golf. Very fair, proper, good test.
"I come in having forgot just how good it was."
Fellow Americans Spieth and Koepka also enjoyed excellent outings on the shores of the Irish Sea, while home hope Paul Casey's 66 put him well in contention, alongside compatriot Ian Poulter (67).
Charley Hoffman was another to reach five under with three to play, but he gave strokes back on the 16th and 17th to fall two shots off the pace.
Meanwhile, defending champion Henrik Stenson carded a 69 and Rory McIlroy fought back from being five over through six to sign for a battling 71.