In the Boat Race, more than any other rowing event, the cox can make the difference between winning and losing.
The cox is the only team member who sees where the boat is going
Not only does he have to steer the boat, but the cox must also be the one to control the pace of the race - and motivate his team-mates when they feel like giving up.
The coxes of the 2006 race, Peter Rudge of Cambridge and Seb Pearce of Oxford, describe their jobs and the extra pressures of the event on the Thames.
Rudge: The first thing you've got to do when you're starting out is shut up and steer straight, then you pick up the rest gradually.
Every time you put the rudder on, the boat slows down so any cox has got to learn to steer in small movements.
The Boat Race course is four miles 374 yards, much longer than the international standard 2,000m (1.24 miles)
Coxes steer with a pulley system connected to the rudder
Push forward on the left and the boat turns to the left, and vice versa
Coxes aim to steer the fastest line, taking into account the tides and the river bends
Most novice coxes spend all of their time pulling the rudder strings and that really messes up a crew.
Pearce: An eight is just too big for a rower to steer [pairs and most fours are steered with a foot plate] so that's really why the cox is there.
Pearce: In a normal race, the cox's first job is to steer straight, but mainly to execute the race plan and react to what the other crews are doing.
With a 2,000m race, you can pretty much plan it out and have calls for extra effort or technical focus at certain points.
Rudge: You're basically a coach sitting in the boat so you've got to have a very good understanding of how to row, and the technique the coach is trying to get the crew to row with.
SHADES OF BLUE
Peter Rudge (Cambridge)
Took up rowing at King's School, Chester. Part of the GB squad since 2001. World bronze medallist in 2001, silver in 2003. Coxed losing Cambridge boat in 2005
Seb Pearce (Oxford)
Drafted in late for his knowledge of the course after four years at Imperial College, London. Second in Head of the River Race (the Boat Race course in reverse) in 2005
A lot of coxes just shout things mindlessly and if you do that you're really not helping anyone.
Rowers get tired and they get stupid when they get tired. They can't take in too much and it really comes down to three or four words they pick up on. Everything else you can cut straight out.
Most of what I say is tactical or technical, because you don't need extra motivation in the Boat Race. Just to get to the start you have to have the motivation.
People have different responses to different things. Some people tense up naturally and need to be calmed down. Other people need to hear more aggressive words. You have to get a balance for everyone.
HOW THE BOAT RACE DIFFERS
Rudge: When the guy says 'Go', the roar that you get from the crowd is hard to comprehend until you've done it.
What the crew can hear from you is quite limited in the first few minutes, so you've got to have key words at key times that they can hear. After 25 strokes you say 'backs' and everyone starts pulling their backs through.
It's autopilot for the first two minutes, then it gets a little bit quieter and you can tell what's going on.
I've been rowing on the river for years but as part of the Boat Race programme you spend an awful lot of time in boats and in launches going over the course and we have a coxing coach, Alan Innes, who does that with us.
Pearce: In the Boat Race the cox is trying to juggle a lot of information that's going on around, trying to react to what the umpire's saying.
The Thames is tidal with a stream. The umpire has a view on where the fastest water is and wants us either side of that fast line.
The winning cox traditionally gets to take a dip in the Thames
We have to react to what the umpire's saying but also get the best of where he allows us to go.
You don't want to move too much because that will take you out of the fast water but coxes who don't listen to umpires come a cropper. The best I can do is get the crew down the course safely.
It's a long race and the condition changes a lot with the wind and the bends. The way the crews row changes a lot so we're trying to manage whether they're rowing well at any time.
Because the race is so long you can only have a race plan for so long and a lot of being a cox in this race is trying to read it and make tactical moves at the right point.
I have an artillery of calls that I can tell the guys when we hit certain situations, but you've got to be dynamic and manage the situation.