Mercedes has been working hard to bring down the weight of its W08 challenger, after starting the campaign struggling to get near the 728kg weight limit for car and driver.

Although improvements have been made over the course of the first five races, the team still needs to find further savings so it can start using ballast to help better balance the car.

So on the edge is Mercedes, and so close is the fight with Ferrari, that Hamilton has elected to sacrifice having drinks during the race to help save a bit more weight.

The lack of liquid will help shave off a vital kilogramme or two at the start of the race.

The lack of drinks could explain why Hamilton sounded so out of breath during stages of the Spanish Grand Prix, as he was pushing to the maximum in his fight against Sebastian Vettel.

Asked after the race to explain the physical challenge of racing the 2017 cars, Hamilton said: "I think it's dependent on what kind of race you have.

"A lot of the races that we do with the type of racing that we sometimes have to do, where you're saving fuel, like in the last race for example [in Russia], I couldn't push because the car was overheating.

"Whereas today it was... from Turn 1 to the end, it was flat chat. You're just using everything you've got so for sure, in that first stint, for instance. To stay on Sebastian was a killer.

"Also I don't carry drinks in my car either to save weight, so I'm not having a drink through the race. And then at the end, I used everything I had left when I jumped into my team and my heart rate hit the ceiling.

"I was good when I got out of the car but jumping into... I don't know if I will do that again. I was a little bit tired after that one."

Mercedes boss Toto Wolff said he was not concerned about Hamilton sounding so exhausted on the radio.

"I think it was just an expression of how hard he was pushing," he said.

"When you need to follow a car that close behind, you obviously haven't got the aerodynamic benefit of the guy in front. That is difficult. He gave it all and you could hear it on the radio."