How can I persuade auctioneer to let me buy by private contract?

Tax Planning and Financial

Hi,

I would like to buy a property which failed to sell at auction and the auctioneer wants me to pay a 10% deposit and then complete within 28 days. It would suit me better to buy by private contract, using a mortgage.

Can anyone please advise me of the best arguments that I can use to turn this into a private sale? I guess the auctioneer wants his chosen process because it's faster and he understands it better, and he won't loose face in front of his vendor. Is it financially better for him to sell under the terms of an auction even if he does not get commission on the bridging loan fees?