For almost four years, Paul Massey, 53, Britannia's general manager in London, and Alan Curtis, 49, his second-in-command, told 20 tour companies that they could only charter aircraft through a middleman.
But the middleman, aircraft broker Henry Wolff, 69, was part of their conspiracy. And, while Massey and Curtis produced documents with one price for Britannia's accounts - less the fake commission - Wolff invoiced customers for a higher amount and diverted the difference to a Swiss bank account.
Massey, from Earlsfield, south-west London, Curtis, from Bournemouth, and Wolff, from Pinner, Middlesex, have each pleaded guilty to conspiracy to defraud. They appeared for sentencing yesterday at Southwark Crown Court, but the hearing was adjourned until today.
Police, who were tipped off, believe the men may have netted more than £1m.
After the fraud was discovered, a secret package of evidence - thought to have been sent to Britannia's solicitors by a lover spurned by Massey - led police to the money.
Lawyers and detectives, led by Detective Inspector David Crinnion, recovered £326,321 from Massey's Swiss bank account and confiscated a house in Colliers Wood, south-west London, a £125,000 flat in the West End of London, and a £60,000 plot of land in Alsace, France. They also recovered more than 2 million French francs (£250,000) from another account.
When he was confronted by police, Curtis, Britannia's scheduled flights project manager, returned £99,855 and told detectives he had spent about £40,000. In a subsequent civil action, Mr Wolff returned £260,000.
Yesterday, David Farrer QC, for the prosecution, told Judge Geoffrey Rivlin QC that from January 1988 to December 1991: "The defendants dishonestly abused arrangements to pay brokers' fees to Wolff in order to secretly channel large sums to Massey and Curtis. These were sums to which both these men knew they were not entitled and for which, as they knew, they were accountable to Britannia Airways, their employer."
Mr Farrer said Massey opened accounts for all three men at Credit Suisse bank in Zermatt near Zurich. He was also the sole signatory to an account in the name of Wald Reisen which sent invoices to Wolff's broking firm in Pinner. No services were ever provided by Wald Reisen, but the invoices, totalling £326,321, helped explain the movement of so much money out of Wolff's business.
Representing Massey and Curtis, Stephen Batten QC and Frank Abbott said the men had no idea how large their secret profits would be when the venture started.Reuse content