By Andy Green GBR Challenge's starting helmsman explains the finer points of driving an America's Cup boat

Green puts England bowler Darren Gough through his paces

I specialise in the cosmic dance that is the pre-start in the America's Cup.

This is the five minutes before the gun where you can deliver a sucker punch to your opponent or lure them into a mistake.

These boats are 25 tons of lead and carbon, with a huge sail area and lots of momentum.

They come together extremely quickly so the helmsman needs very good judgement to be able to calculate in a split second the time it will take to cover a certain distance.

You need a good deal of aggression, a slightly detuned nervous system and sometimes you need a liberal dose of chutzpah.

But the key to match-racing is to be able to manage your emotions and strike a balance.

Sometimes you have to be bold where you can see an opportunity for a gain but you also have to be wary that if you are too aggressive you might incur a penalty or put yourself in a worse position.

And it goes without saying that you have to have a very close knowledge of the rules.

You have to know when you are at risk, when you have the right of way and understand how best to use the rules to the best of your advantage.

In the pre-start you have to be able to see the entire picture.

Ultimately the most important thing is to start on the line, having won the side you want and ideally fractionally ahead which will give you a slight jump for the rest of the race.

We have gone through countless scenarios in the classroom and have done a lot of in-house racing.

We have a pretty good idea of where we want to be and how we want to manage ourselves in pre-start.

But undoubtedly emotions run high.

You have five minutes to prove yourselves in the heat of battle before the boat-speed race begins on around the course.

For me then it is a question of handing over the wheel to the skipper, Ian Walker.

I then become the strategist, backing up the tactician with input on the wind and the opposition.

The on-course helmsman requires a slightly different mentality.

He is a speed technician, with a feel for squeezing every half knot out of the boat.

And you have to be able to concentrate hard for three hours whereas I just give it heaps in five minutes.