Aided by James Cracknell in the bow and Tim Foster in the No 3 seat, the British four's victory gained the two points needed to win their event.
The coxless pair of Bobby Thatcher and Ben Hunt-Davis also emerged triumphant after squeezing past the Australians in the last 500 metres without recourse to a big push. Thatcher said: "I could sense we were rowing better and could go through at any time."
The men's lightweight eight, fresh from a thrilling win by a distance of one foot in the Ladies' Plate at Henley, built a progressively bigger lead over Germany to win a place in the final by four seconds.
Greg Searle, who has turned from rowing to single sculling, showed the benefit of his victory last week at Henley when he finished a comfortable second to the 1995 champion, Iztok Cop of Slovenia. Searle has the strength and nous of a world-class sculler, but earlier this season was too slow off the start to compete for honours.
Guin Batten dominated her heat of the single sculls and appears fully recovered from the virus which knocked her to a standstill against Sweden's Maria Brandin in the final of the Princess Royal Cup at Henley.
Here, the Belorussian Ekaterina Khodatovich looked the strongest, with three scullers in a group behind her. Batten will have to be at her sharpest in the semi-final to be sure of a place in the last eight tomorrow.
Her sister Miriam, the first British woman to win a World Championship medal in 1991, has been searching ever since for another major victory. She is now in a double scull with the tall Scot Gillian Lindsay, which led the first 1,000 metres of the heat before fading to third place, five seconds behind the Swiss. In contrast to Searle the pair need to learn how to sustain raw speed over the entire 2,000 metres of a race.
The other half of the women's team, the pair of Dot Blackie and Cath Bishop, raced to second place behind the new Canadian crew but they were so far clear of the rest of the field that there was little to demonstrate any improvement in their second-place form at Paris two weeks ago.