Adam Peaty fired out a major warning to his Olympic rivals in Rio by breaking his own 100 metres breaststroke world record in the heats on Saturday.
The 21-year-old, hotly fancied to become Britain's first male Olympic champion in swimming since Adrian Moorhouse in 1988, came home in 57.55 seconds.
The time was 0.37secs faster than the record he set last year.
Peaty went into the opening day of competition at the Olympic Aquatics Stadium as world record holder, world, European and Commonwealth champion in the 100m breaststroke and, as a statement that he is out to add Olympic gold to the collection, this was as emphatic as they come.
He was well over a second quicker than Yasuhiro Koseki, the second fastest qualifier for the semi-finals. In fact there was less time separating Yasuhiro and the 16th and final fastest qualifying mark than between the Japanese and Peaty. The gold is surely the Briton's to lose.
The Uttoxeter swimmer admitted such a fast swim in the heats had "definitely not" been in his plans, but he insisted he could go even faster in the semis on Saturday night, with the final following on Sunday.
"Hopefully tonight we are going to move it on a little bit more and see what we've got," said Peaty, the three-time world champion who was afraid of water as a child.
"Hopefully I'm going to feel a lot better and swim a bit faster. We are not going to get too complacent now, we are going to keep striving, keep pushing the boundaries and see what we get.
Britain's swimmers won just three medals at London 2012, but already there were good signs for Rio.
Ross Murdoch qualified alongside Peaty for the 100m breaststroke semis in joint ninth in 59.47s, but Ireland's Nicholas Quinn went out.