Red Bull technical chief Adrian Newey revealed he was scared for his drivers' lives in the Belgian Grand Prix yesterday - after sending them out to race on potentially dangerous tyres.

While Red Bull petitioned to be allowed to replace the front tyres after qualifying, the FIA determined that the risk was not significant, and that it was caused by Red Bull's set-up choice and not by accident.

Formula One regulations only permit tyre changes between qualifying and the race if tyre damage is due to an accident or a fault with the tyre.

Red Bull were given the option to change the tyres and start the race from pit-lane but declined.

Newey experienced death at close quarters in 1994 when he designed the Williams car in which Brazilian legend Ayrton Senna was killed at the San Marino Formula One Grand Prix.

He admitted he had his heart in his mouth throughout the 44-laps race on the spectacular high-speed Spa circuit.

And he said he felt relief rather than joy at the end of the race when his driver, German Sebastian Vettel, the series leader and defending champion, won ahead of his Australian teammate Mark Webber in a commanding one-two triumph.

Newey said: "Pirelli were telling us after qualifying that our tyres were very marginal and they wouldn't say whether it was after half a lap or five laps, but they were going to fail.

"I have to say it was one of the scariest races I've been involved in, it was heart-in-the-mouth stuff, as first and foremost our duty of care is to the drivers' safety.

"And trying to make that call in making sure the car was safe, while not handicapping ourselves from a performance point of view, was quite a difficult judgment to make.

"Frankly at the end of the race I was very relieved that both our drivers were safe."