Content to wait until the last length of the 200 metres freestyle, Palmer then powered his way to victory in a time of 1min 48.85sec, just one-hundredth of a second outside his own British record.
The victory was a surprise to everyone but himself. "I never really envisaged anyone beating me," he said. "I knew that if I was up there at 100 metres they were not going to get away. I felt in control and confident of gold."
Palmer took a long break from swimming after winning an Olympic silver medal in Atlanta last year, disillusioned by the lack of support he was receiving. But a move with his coach, Ian Turner to the elite training village at the University of Bath in January provided the ideal training environment to refocus on winning gold here. Having won an event traditionally used as a warm-up for his favoured 400m, Palmer will be the hot favourite to win a second gold in the longer distance on Friday.
Palmer was nearly joined on the podium by Edinburgh's Jamie Salter, who was denied a bronze by just one hundredth of a second.
He was the second Briton to miss a medal by a narrow margin, after Susan Rolph in the women's 100m freestyle. Later, the women's 4 x 200m relay team had to settle for fifth place, but at least they had the consolation of a British record in 8min 9.44sec.
Michelle Smith, the triple Olympic gold medallist who is now swimming under her married name of De Bruin, won her first gold of a possible six this week in the final of the 400m individual medley.
In typical style, the Irishwoman surged into a two-second lead after the 100m butterfly leg, was caught after the breaststroke at 300m but cut her challengers adrift in the final 100m freestyle.
The 15-year-old Ukrainian European junior champion Yana Klochkova was the nearest of them at 300m mark, as De Bruin had anticipated. "I thought she would be there and I had to work hard down the breaststroke then I had two choices - either let it go or put my head down and fight for it. She wanted to beat the Olympic champion and I wasn't going to let her," De Bruin said.
Getting way from her competitors proved easy compared with escaping the scrum who followed her to her press conference, where the drug allegations that have been made against her since her Atlanta success continued to dominate. She continued to side-step the issue.
Klochkova hung on to finish an impressive second, but Britain unveiled their own promising 15-year-old medley swimmer in Portsmouth's Samantha Nesbit. The youngest member of the British squad here, she showed no sign of nerves at her first senior international competition. Attacking her 400m from the start, she swam a personal best time of 4:51.25 in the consolation final and looks likely to threaten Sharron Davies' 17- year-old record, set at the Moscow Olympics when she won the silver medal, in 4:46.83.
What De Bruin could do single-handedly lead the most successful Irish team ever, the British will need a full team effort to do the same. Hopes for more medals tomorrow lie with the two butterfly specialists James Hickman and Stephen Parry, Karen Pickering in the 200m freestyle and Britain's best chance for a second gold, the men's 4 x 200 freestyle team. Palmer has already taken a step towards history with the first ever medal for Britain in the 200 m freestyle and his performance will lift the others through the week.
It is now possible that the British team will surpass the three gold medals last won in 1987 in Strasbourg.
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