A man found guilty of stowing on board a plane and trying to steal £1.5m worth of pesetas has been warned he faces a long jail term.
Watson's plan failed when handlers dropped the crate in which he hid
Rawson Watson, 37, of Marlborough Road, Gillingham, Kent, had denied the charge of attempting to steal the cash from a plane at Heathrow Airport.
During the two-week Old Bailey trial, the jury heard Watson planned to smuggle himself and the money away in two specially-constructed express handling boxes.
He had hidden in the lining of the cargo hold of the Boeing 767 during a return flight to Madrid in January 2000.
Obviously, I have in mind a
lengthy custodial sentence - the question is how long
Recorder of London Judge Michael Hyam
But the court heard his "cunning and daring plan" was foiled when loaders dropped the box in which he was hiding and he tumbled out.
Watson then ran off empty-handed across the tarmac.
The Recorder of London Judge Michael Hyam warned: "Obviously, I have in mind a lengthy custodial sentence - the question is how long."
He added: "I am a little concerned - I know absolutely nothing about him."
The jury of eight women and four men took more than eight hours to reach its verdict, by a majority of 11 to one.
Graham Trembath QC, defending, said: "There is little I can say - it is so unique.
"It was described by the Crown as a cunning plan, but fate played its part.
"He cut his finger and was toppled out of the box."
Watson was identified nearly three years later by DNA analysis of the blood left at the scene.
He was stopped by the police for drink driving - and was then found to be a billion-to-one DNA match for the blood found on the plane.
Mr Trembath said Watson had been a "foot soldier" in the Heathrow heist, with the crime being planned by others.
Watson had 12 previous convictions for 33 offences and was jailed at the Old Bailey in 1993 for eight years for two robberies.
One involved tying up the manager of a hotel in Oxfordshire and in the second, while on bail, he acted as the look-out for a robber with a fake gun at a Post Office in London.
In his defence, Watson had told the court the man in the box could not have been him because he was backpacking in Africa at the time.
He was cleared of a second charge of damaging an aircraft at the Old Bailey on Friday.
He has been remanded in custody until 4 July for a pre-sentence report.