With his slicked-back grey-streaked hair, impeccable suits and a penchant for being helicoptered to mountain peaks on luxury skiing holidays, Luis Barcenas is the cool-headed moneyman viewed as the greatest threat to Spain's ruling Popular Party.
The 55-year-old former party treasurer also faces multiple corruption probes.
But the man whose face is regularly splashed on the nation's front pages and broadcast on its television screens shows few outward signs of worry.
Last month he even flew off for a spot of heli-skiing at a Canadian resort during a break between court appearances, and on his return he greeted waiting reporters at Madrid-Barajas airport with an obscene gesture: sticking up his middle finger.
Many in Spain suspect his confidence stems from sensitive secrets he may hold about the finances of Prime Minister Mariano Rajoy's party; he was its treasurer until 2009 and the accounts manager from 1990-2008.
Barcenas has been under investigation since 2009 in the so-called Gurtel case, a business and political corruption scandal related to contract awards, allegedly reaching into the senior ranks of the Popular Party.
But he really hit the national headlines in January when the conservative daily El Mundo, citing five "reliable sources", said Barcenas had for years used a slush fund to make undeclared payments to leaders of the Popular Party.
Soon after, the left-of-centre daily El Pais splashed on its front page photographs of handwritten account ledgers purportedly drawn up by Barcenas, who was also a senator from 2004-2010.
Baptised the "Barcenas papers", they show donors and alleged recipients, including Rajoy himself supposedly receiving up to 25,000 euros ($32,000) a year between 1997 and 2008.
The prime minister has flatly denied receiving any such money. Barcenas denies being the author of the papers, which he says are a fake.
Since the allegations emerged, however, two judges at the National Court have opened investigations: Barcenas will testify before both on Friday.
"He is calm because he thinks he has information that is very sensitive for the Popular Party and he is threatening to drop the atomic bomb and lift the lid on irregular financing if he has judicial problems," Esteban Urreiztieta, chief editor at El Mundo, told AFP.
"He is cold, calculating and very punctilious, so he wrote down all the operations. Nevertheless, despite his proud and smug appearance, he would crumble if he went to prison," he said.
The paper's deputy director, Casimiro Garcia-Abadillo, agreed that Barcenas believed he could pressure the ruling party.
"Everything depends on Barcenas, if he wants to push the accelerator he can create a real mess," Garcia-Abadillo said.
After 20 years in key posts, Barcenas holds "a great deal of information and he is ready to use it" if he feels abandoned, the El Mundo deputy director said.
Barcenas, holder of a Swiss bank account in which he reportedly says he stashed up to 38 million euros supposedly made from buying and selling paintings, "has told the people around him that there is absolutely no way he is going to jail", Garcia-Abadillo said.
Others, like Barcenas' friend Jorge Trias, former member of parliament for the Popular Party, say that when Barcenas was the party's accounts manager he simply "received instructions".
Spaniards, crushed by austerity measures, recession and a 26-percent jobless rate, are glued to the daily developments of the Barcenas scandal as it if were a soap opera.
Barcenas rarely lets them down.
Suing the Popular Party for "unfair dismissal" he revealed that the party, which had claimed it severed links with him three years ago, actually paid him more than 21,000 euros a month from March 2010 to January 2013 as a "consultant".
During this time he kept an office in the party headquarters from where, earlier this month, he said two portable computers had been stolen.
According to Spanish media, Barcenas' lawyer submitted evidence that his client had declared 11 million euros in his Swiss bank account under a controversial tax amnesty.
In reply, the Popular Party has issued various, sometimes confused, denials.
"Everything relating to me and my colleagues is untrue, except for a few things," said Rajoy.
The Popular Party's number-two, Maria Dolores de Cospedal, tried to explain away the party's payments to Barcenas until January this year as "deferred severance pay".
Sources close to the party say the scandal has split members between those who want to make a clear break from Barcenas and those who want to safeguard him.
"If the Barcenas case ends up being proven, especially as it relates to Rajoy, it would be unbearable for the Popular Party, which could be pushed to renew its leadership," said Gabriel Colome, political analyst at Barcelona's Universidad Autonoma.