"We are very, very nervous," said a member of one of the final consortia. "The Agency has done very well and is playing this tight to its chest."
The announcement will be a couple of weeks later than expected. "The Agency had extra questions for all the bidders which we've responded to. Now we just wait," said another consortium member.
Costs of the bids have been affected by the credit crunch, said one consortium's banker.
"It's more difficult to find money to borrow and when you do, it costs more," he said.
"The big issue is that normally we'd look to lay off some of the debt if we won the bid and no one's going to want it now which leaves all the risk with us for the present."
Around £2bn will need to be raised for the M25 widening this year, according to City sources.
Highways Agency finance director Mel Zuydan is on record as saying he is comfortable that finance will be available but that it is likely there will be a premium to pay.
Three construction and finance groups have tendered for the 25 year concession. They are: Connect Plus (Balfour Beatty, Skanska, Atkins and Egis Projects); Flow (Vinci, Autoroutes du Sud de la France, Laing Roads, Carillion, Costain, Ringway, Mouchel, Norwest Holst and Jacobs); and Amey, Laing O'Rourke and Ferrovial Agroman.
All have their advantages. Connect Plus members Balfour Beatty and Skanska have worked successfully together on the M1 widening; Flow members Carillion and Mouchel currently manage the M25 for the Highways Agency as Sphere; while Amey is one of the Agency's most prolific network managers and Laing O'Rourke a prized new entrant to its supply chain.