Gerhard Gribkowsky, formerly in charge of the state-controlled Munich bank BayernLB, is the star witness, and on Tuesday he backed prosecutors' claims that Ecclestone paid up to influence the sale of F1's commercial rights.
"This role (of F1 chief executive) is his life. Of course he wanted to keep it," Gribkoswky, jailed for eight and a half years for accepting $44 million, is quoted by German reports as having told the court.
He said that Ecclestone had once said he would rather "die in a puddle of fuel" than lose his post in control of formula one -- an alleged statement that was immediately disputed by the diminutive Briton's lawyers.
Gribkowsky, however, depicted Ecclestone as someone determined to keep running F1, operating in the sport as requiring others to "have no other gods before me".
Interestingly, Gribkowsky did not deny Ecclestone's defence that he was being put under pressure over his personal British tax affairs.
Ecclestone says that is the only reason he paid the 56-year-old German.
"We didn't have anything concrete (about his tax affairs)," Gribkowsky told the court. "It was mainly nuisance value."
He revealed that he was also questioned just weeks ago about Ecclestone's tax affairs by the British authorities.
"I told them what I told this court," said Gribkowsky.
"I didn't have any inside knowledge but I used the issue at the time to put pressure on Ecclestone to make him settle litigation over formula one," he added.