Martin Whitmarsh, McLaren's team principal, feels the British Grand Prix will serve as a litmus test for his team's title push.
McLaren are due to unveil their own version of the blown diffuser that has proven so successful for Red Bull Racing this season.
Ferrari, Mercedes and Renault revealed the first version of their concept in last Sunday's European Grand Prix as the teams attempted to keep pace with Red Bull, who have been on pole in eight of nine race this season.
Although McLaren have struggled over one lap, their race pace has ensured they lead the way in both the drivers' and constructors' championships.
If their blown diffuser proves as successful as the Red Bull model, and delivers the time gains the team expect, it could become Lewis Hamilton versus Jenson Button for the drivers' crown.
"The upgrade was planned for [the German Grand Prix on July 25], but all being well we will have it for Silverstone," Whitmarsh said."But the British Grand Prix is an important race for us, and at a circuit like that we have to be competitive with Red Bull if we are going to be able to beat them this year.
"If we can be competitive there then we have a good chance to win both championships.
"It will be a big race, but it will not be the end of it whatever happens. If we beat them they will not stand still, and if they beat us we are not going to stand still. I hope it will be close - certainly closer than last year."
On that occasion Sebastian Vettel spearheaded a Red Bull one-two, while for McLaren it was the last race Hamilton had to endure with an abysmal car, with the Briton finishing 16th.
So it is with some pride McLaren go into this year's Silverstone showdown on July 11 with Hamilton leading the standings by six points from Button, and with McLaren 30 points clear of Red Bull.
"To come out of Sunday's race in Valencia with a second and a third was fairly reasonable," Whitmarsh added. To come out of it leading both world championships, having seen what the others have got and with our decent upgrade to come, we must believe we are in the position to have a strong second half to the season."
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The specs
Engine: 2.7-litre 4-cylinder Turbomax
Power: 310hp
Torque: 583Nm
Transmission: 8-speed automatic
Price: From Dh192,500
On sale: Now
RESULTS
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SPECS
Engine: Two-litre four-cylinder turbo
Power: 235hp
Torque: 350Nm
Transmission: Nine-speed automatic
Price: From Dh167,500 ($45,000)
On sale: Now