A raffle featuring four top-class prizes was very well supported, with £2,900 raised.
But just as host Mike Brewer was revealing to the room how much was raised, The Auto Network managing director Anton Hanley said he would double the figure.
That means £5,800 will be passed to the hospital.
Anton said: ‘It was a spur-of-the-moment decision but I was delighted to be able to do it.
‘Great Ormond Street is a superb cause and deserves our support.’
Car Dealer magazine editor Colin Channon said: ‘It was a lovely gesture by Anton and The Auto Network team, and very much appreciated.
‘People at the awards had already dug deep to raise £2,900, but to have that figure doubled was the icing on the cake of what was a tremendous evening.’