Six men and two women appeared in court this week charged with laundering the stolen millions by filtering it through different Nigerian bank accounts.

Southwark Crown Court heard that the original con was a “simple and straightforward invoice fraud”.

The Independent reported that a man using a false name wrote to the ODA claiming to represent Skanska, and informing them that the company bank account had been changed.

The ODA promptly transferred £2.3m it owed into the bogus account on 27 May 2010.

James Dawes, prosecuting, said the gang targeted Network Rail, Dorset County Council and two building firms with the same ploy.

But their plan was foiled within days and only the transfer from the ODA and £86,645 from one of Skanska’s suppliers ever went through.

Dawes said: “Although the plan was to steal £6 million, they in fact only stole about £2.4 million because some of the companies, the authority and the council became alert to the fraud at a reasonably early stage”

All the defendants deny money laundering.