Contenders for Great Britain's Olympic boats will be putting their Athens aspirations to one side to represent their Clubs at the annual open event for men's eight oared crews.   Great Britain's pride is also at stake, since over forty overseas Clubs with 65 crews are challenging for the Headship and Fairbairn Trophy.  Club eights from Germany, France and a record eleven other nations will compete. Another dimension is the strength in depth on display.  420 crews (or nearly 4000 competitors) mean the race is again greatly oversubscribed.  Elite full-time athletes, clubs, schools, colleges and more recreational participants will all participate in the gruelling four and a quarter mile race. Leander Club are the current Head and their top crew, which typically forms the nucleus of the Great Britain Team, includes triple Olympic gold medallist Matthew Pinsent and his fellow Sydney crewmate James Cracknell.  Another strong contender on home waters is Imperial College, fielding seven crews, the top of which contains several World and Olympic medallists.  The Race is run as a processional time trial and is a great, free sporting spectacle on the Thames. Racing starts at 3.45 pm and continues for about one and a half hours. Further details and results will appear on www.horr.co.uk.