The executive who helped Lord Black build his media empire from its humble Canadian beginnings has taken the stand as chief prosecution witness.
David Radler's testimony is crucial to the prosecution's case
Once head of operations at Hollinger International, David Radler, 64, admitted fraud in 2005 in return for a reduced 29-month jail term.
Prosecutors hope his testimony will seal the case against media baron Lord Black, who faces charges of fraud, racketeering and obstructing justice.
Lord Black denies all wrongdoing.
Mr Radler testified he met Lord Black in 1969, an event that marked the birth of one of the largest newspaper holding companies in the world - Hollinger International.
"I was impressed with Mr Black's knowledge and his ability and I thought that he would be a great partner to have," Mr Radler told the Chicago court.
15 charges of fraud
one of obstruction of justice
one of racketeering
Federal prosecutors allege Lord Black
Fraudulently received non-compete fees from the sale of Hollinger International assets
Deprived the company of his honest services
Repeatedly benefited himself at the expense of the company and its public shareholders through the abuse of company perks
Other executives on trial
John Boultbee - former chief financial officer
Peter Atkinson - former general counsel
Mark Kipnis - former corporate counsel and secretary
He recalled how he and the British peer bought a loss-making English-language newspaper in the French-speaking community of Sherbrooke in Quebec for $50,000 (£25,000) and made it profitable in three months.
Mr Radler testified that major financial and business decisions were made "jointly" and, at the time, him and Lord Black were "equal partners".
At issue is whether or not the former chief executive of Hollinger and his associates, John Boultbee, Peter Atkinson and Mark Kipnis, enriched themselves at the expense of shareholders with non-competition payments through the sale of hundreds of its community newspapers.
Defence lawyers are expected to portray Lord Black's former right-hand man as one of the main culprits in the scandal that rocked Hollinger International, which owned titles such as the Jerusalem Post and Chicago Sun-Times.