In past years the crews have squared the blade in the water on the word "attention", ready to pull cleanly on the final command. This, with the water flowing past the hull, means the the boat has been dragged forward, stretching the stake boat men's arms and sometimes giving a small but still unfair advantage for one side.
The warm-up to this year's Boat Race is enhanced with a brilliant line- up for the World Sculling Challenge over the same course this afternoon. At 3.30pm a field of five of the top women scullers, including Ekaterina Khodotovich, the 1996 Olympic champion, will race off, followed half an hour later by five men, four of whom are former world singles sculls champions at heavyweight and lightweight.
The Challenges are a revival of the match races which dominated the sport on the Thames for 200 years before dying out early this century. Today's race is the seventh since the revival and the first since the sport's amateur code was abandoned. The present qualification is that the entrant must be an Olympic or World singles sculling champion such as Giovanni Calabrese of Italy, or, like Guin Batten of Britain, a former Thames World Sculling Trophy holder.
The greatest risk to such a distinguished group is the Bank Holiday river traffic. The Putney-to-Mortlake reach will not be closed to other users as it is for the Boat Race, and with strangers unfamiliar to the river and its unexpected hazards this could be a disastrous combination.
The four-and-a-half mile distance and the subtleties of the fast stream which is found where the river runs deepest mean that the normal rule of power over skill is reversed, with watermanship and tactical wit more likely to prevail.
Among the men the only local, Greg Searle, the first British sculler to win a World medal since the war, has dropped out with a back injury, leaving Jamie Koven of the United States and Derek Porter of Canada as the bigger men, with Iztok Cop of Slovenia - the winner in 1995, who was only released from military duty yesterday - as the slightly smaller man.
He denied that his late arrival is due to the Balkan crisis, saying, "No, it is just that my commander is a fool."
The men's line-up is completed by Calabrese and the other Italian Stephano Basalini, the 1998 lightweight champion.