The title-holders go into tomorrow's final as fastest qualifiers. Nudging ahead just after the start, they were a length ahead by half-way on the 2,000-metre course.
The Australians came through from a slow start to overtake the World Cup winners, Romania, and appeared about to threaten the Britons. but Redgrave called to raise the pace and his crew spurted clear before slowing across the line.
"We wanted to make sure of winning. The others were in a tussle behind us over that last 1,000m and we just wanted to make sure we were first," Redgrave said .
In other races, the three-times lightweight sculling world champion, Peter Haining, qualified second in his semi. The ebullient Scot raised his fist high with 100m to go as he broke Switzerland's Michael Banninger after a race-long battle for qualification behind the Italian Stefano Basalini.
Haining, who missed last season through illness, felt hard done by in the lane seeding and was making the point to the officials. He paddled leisurely across the line and now believes that despite his setbacks and his 36 years he can take the title for a fourth time.
"They didn't deserve to be in the final," he said of those who trailed in behind him. "They quit. They didn't want it enough."
The sculler Guin Batten beat Trine Hansen into second place, and Miriam Batten and Gillian Lindsay, silver winners last year, won their double sculls semi.
Greg Searle went through in the men's sculls finishing third in his heat, and so too did Britain's find of the season in the coxless pairs, Steve Williams and Fred Scarlett.
Searle, third in the world last year, had three former champions in his semi-final, but as usual also has the attitude to conquer when it matters. No serious judge of form would have given him an outside chance of a place in the final on the evidence of the summer's racing, but in Cologne he has looked better in each round, and yesterday had the gift of the American, Jamie Koven, on whom his race focus was trained, breaking an oarlock just outside the first 100 metres and stopping. Searle, who has never failed to win a medal since 1990 is, amazingly, back in the hunt.
The best result of the day belonged to Scarlett and Williams. They are both graduates of the Oxford Brookes University, which threatens to overtake its older neighbour as a centre of sporting excellence. They should have been out of their depth at this level but never gave it a thought and chased the World Cup winners, West Germany, home for a place in the top six at their first attempt.
Results, Digest, page 25