The sacks of stolen cash have not been recovered.
The third trial in the case of an armed robbery of a cash depot at Heathrow Airport has collapsed after five months.
The February 2004 robbery at Menzies World Cargo netted the thieves £1.75m, which has never been recovered.
Judge Jeremy Roberts told the jury at the Old Bailey the move could not be avoided, despite an estimated cost of bringing the trial of £22m.
The four accused will appear next week to set a new trial date.
The reasons behind halting the trial and dismissing the jury cannot be reported.
Alleged robber John Twomey, 60, of New Milton, Hampshire, will now face his fourth trial.
Co-accused Peter Blake, of Notting Hill, and Barry Hibberd, of Shepherd's Bush, both in west London, will be tried for the third time.
A fourth man, Glen Cameron, of Kenilworth Road, New Milton, will be tried for the second time.
All four men deny charges of conspiracy to rob and to possess firearms.
During the raid, six masked men rounded up members of staff at gunpoint in what police allege was an "inside job", the court was told.
Mr Twomey first faced trial in 2005 when proceedings against him were stopped for health reasons.
He was retried in February 2007 alongside co-accused Mr Blake and Mr Hibberd, but after the six month trial, jurors were unable to reach a verdict.
The third trial, this time with co-accused Mr Cameron, began in July of this year.
Judge Roberts thanked the jurors for their service.
"In the course of a major criminal trial like this one, events sometimes occur which create the risk of real injustice or unfairness to one side or the other and sometimes those events are so serious that the trial cannot continue.
"That is what has happened in this case. It wouldn't be appropriate for me to give you any further information about what has occurred."