Four men have been jailed for making more than £1.3m worth of counterfeit £10 notes.
Brothers Amrit and Prem Karra were each sentenced to seven years for using their printing business in Hockley, Birmingham, to produce the forgeries.
Rajiv Kumar and Yash Mahey were jailed for four years at Birmingham Crown Court for counterfeiting money between September 2011 and February 2012.
The court was told £1.27m worth of fake notes had been recovered by police.
All four were found guilty of conspiring to counterfeit a currency note with the intention they or another would pass or tender it as genuine.
Prem Karra, 43, from Brookhouse Road, Walsall, ran Karra Design and Print on Summer Lane with his brother Amrit Paul Karra, 45, of Broadway North, Walsall.
The court heard along with Rajiv Kumar, 40, of Clarkes Lane, West Bromwich, and Yash Paul Mahey, 46, from Granbrook Road, Handsworth, they used computers and machinery to make "high-quality counterfeit notes".
The men worked throughout the night to "avoid detection", the court was told.
The forgeries were found at businesses as far away as Kent and south Wales, during an investigation by the National Crime Agency.
It said the fakes, some of which had their own unique serial numbers, were still being discovered by banks and retailers.
The court was told the printing company was in financial trouble and the brothers had turned to counterfeiting to save it.
David Emanuel, defending Prem Karra, said: "The temptation of a cash injection of a job like this was too much.
"It was a very misguided attempt to save the business with a short-term cash injection."
Quentin Hunt, defending Rajiv Kumar, told the court others had been involved in the fraud.
"These four conspirators, you may infer, were by no means the only persons involved in the distribution and production of these counterfeit notes," he said.
Judge Richard Bond said the fact that some of the £10 notes were still in circulation showed how "sophisticated" the operation had been.
"If the notes were passed as part of ordinary day-to-day financial transactions they would go unnoticed unless someone examined them," he said.
In sentencing, he told the men: "You were all professional forgers with carefully prepared plates and machinery.
"The reason for your offending is quite simply greed. You were trying to make a large sum of money."
'Found and punished'
The judge banned the Karra brothers from holding a company directorship for eight years.
Julian Harrison-Pike, whose firm Flaps is located near the printing company, said the brothers were well respected by those who knew them.
"Over the years we have known them I would never have expected it," he said.
"They were a nice couple of guys and the whole family was well thought of.
"I know they were very active in the Birmingham business community."
Richard Warner, the National Crime Agency's Birmingham branch commander, said: "These men ran a sophisticated operation that posed a significant threat to the UK economy at the time.
"By working closely with industry experts our officers stopped them causing more damage."
A Bank of England spokesperson said: "The bank works closely with the National Crime Agency in the fight against counterfeiting. We are grateful for their work in pursuing this case to a successful conclusion.
"Those individuals who engage in counterfeiting should know they will be found and punished for their crimes."