Head of the River Race only open to men's eights and is considered to be the peak of the head race season — attracting the top UK crews as well as foreign clubs. Composite crews, drawn from more than one club or institution, are not permitted. The Championship Course is that of the Oxford and Cambridge Boat Race but, unlike the Boat Race, the Head of the River Race is raced on an ebb tide from Mortlake to Putney. The starting time for the race is different every year and depends on the tide — the first crew (winner from the previous year) starts the
The Boat Race 1846 was rowed on the ebb tide, from Mortlake to Putney. For the first time in the history of the race, both boats used outriggers. Cambridge "rowed in an outrigger built by Searle, 60 ft in length, 2 ft 8 in in breadth", while Oxford's boat was "expressly built for this match by King of Oxford" and 58 ft 6 in long. Both crews had professional coaches: Oxford used John Noulton while Cambridge were trained by Robert Coombes, a champion sculler. It marked the start of the debate over the use of professional coaches which was not resolved until the 1852