Bus companies who claimed they had been wrongly charged Humber Bridge tolls have failed in an attempt to recover the cash.
Buses have to pay £10 to use the Humber Bridge
The Confederation of Passenger Transport UK, which represents bus operators, had made the claim against the Humber Bridge Board (HBB).
It argued the HBB had charged "large buses" passing over the bridge for the past six years without the legal authority to do so.
While recognising "large buses" were not specifically mentioned in the rules which govern the toll bridge, Appeal Court judges have now said that was clearly due to an error.
Lord Justice Clarke said the error could be corrected by the court and the words "large buses" could be "read into" the rules as if they were actually there.
Elizabeth Laing, the confederation's barrister, said the ruling had "very considerable ramifications" and raised issues of "general public importance".
Under Toll Orders made in 1997, 2000 and 2002, Miss Laing had argued, the HBB had no right to charge buses with capacity for 16 or more passengers a toll which now stands at £10 per vehicle.
The confederation claimed its members had paid out around £1m over the years and wanted every penny back.
Lord Justice Clarke said the draftsman had left a reference to "large buses" out of the 1997 and 2000 Toll Orders "by mistake" although it had clearly been intended that they should be charged to cross the bridge.
He said: "It is inconceivable that either the board or the secretary of state intended to exclude large buses from the classes of vehicle expected to pay tolls, especially since the purpose of the tolls was to help recoup the very substantial costs of building the bridge."