A G4S employee demanded £1million from the company and threatened to detonate bombs fitted to its vehicles if he was not paid, a court has heard.
Daniel Garland, 19, denies blackmailing the security giant in a letter sent to the general manager of a depot in Thornaby, Teesside, in January.
Teesside Crown Court heard he was the author of a letter which threatened to blow up vehicles and also "cause harm" to the partner and new-born baby of an employee while the father was at work.
Garland, of Durham Place, Chester-le-Street, denies two counts of blackmail.
Paul Rooney, prosecuting, said: "This case concerns a letter which was sent by the defendant, Daniel Garland, to his employers G4S.
"In the letter he demands £1 million from them and makes threats to cause explosions and he infers he will cause harm to a new-born baby and her mother if his demands are not met."
A G4S van was robbed in December in Middlesbrough and the raiders who got away with a substantial amount of cash have not been caught, the jury heard.
The author claimed responsibility for the raid, named two employees as being "inside men" and said they had been paid so much for their information that he now required a further £1 million, Mr Rooney told the court.
He wanted the cash to be loaded into a red Volvo lorry that would be parked outside the depot the next day.
Mr Rooney said: "The letter went on to state he fitted mini bombs to a number of G4S vehicles as well as employees' vehicles. It was indicated these bombs could be detonated by remote control."
The prosecution said Garland referred to an employee who had just returned to work after the birth of his baby, leaving his partner alone during working hours.
Mr Rooney said: "If payment was not made then the author of the letter and others would be paying them a visit while they were alone."
The message also said the robbers would be heavily armed and were not "scared" to force their way into the depot if £1million in notes was not there for them.
Mr Rooney said: "It was reiterated that failure to load £1million into the lorry, or if the police were present, would result in the bombs being detonated.
"This was blackmail, say the Crown."
The case continues.