All hell broke loose in Biden World the day The Post broke the first bombshell email from Hunter Biden’s abandoned laptop, on Oct. 14, 2020, three weeks before the presidential election his father would win.

“BIDEN SECRET E-MAILS” read the front page exclusive, revealing a 2015 email from an executive at the corrupt Ukrainian energy firm Burisma, thanking Hunter for introducing him to Hunter’s then-VP ­father in Washington.

“Dear Hunter, thank you for inviting me to DC and giving an opportunity to meet your father and spent [sic] some time together,” wrote Burisma board adviser Vadym Pozharskyi on April 17, 2015, less than a year after Joe Biden had forced the Ukrainian government to fire the prosecutor investigating the corrupt company that was paying Hunter $1 million a year.

The story put the lie to Joe’s ­repeated claims that he knew nothing about his son’s overseas business dealings — and risked sinking his presidential campaign.

But as soon as it broke online at 5 a.m., panicked phone calls and messages started flying between Hunter’s business partners and their advisers, even as social media giants Facebook and Twitter moved to censor the story and lock The Post’s account, while candidate Biden went into hiding.

Fear of DOJ probe

In one communication that day, Hunter’s then-business partner James Gilliar, a former British Special Forces officer with ties to UK intelligence services, “calmly reassures an unnamed person who is concerned that “a Senate committee, the DOJ” might start investigating Hunter’s foreign deals and then “Hunter and/or Joe or Joe’s campaign [will] fire a shot at us.”

“It would be crazy to do that with all the information and all the facts we have [but what happens if] they try to make it ‘Oh, we were never involved. That was [Joe Biden’s brother] James’ idea . . . and try to basically make us collateral damage?” the person asks Gilliar in a message provided by a whistleblower to Republican congressional investigators and obtained by The Post.

Gilliar is unconcerned about potential backlash from the Biden family and Joe’s campaign: “I don’t see how that would work for them,” he replies.

“I think in the scenario that he wins they would just leave sleeping dogs lie.

“If they lose, honestly, I don’t think that the Big Guy really cares about that because he’ll be too busy focusing on all the other s–t he is doing.”

The communication, obtained by The Post Wednesday, is significant because it bolsters the claim by ex-Hunter business partner Tony Bobulinski that the Big Guy was a code name for Joe Biden.

The reason the identity of the “Big Guy” is important is because it adds to the weight of evidence suggesting that Joe Biden not only knew about Hunter’s international influence-peddling scheme, but allegedly was cut in for a slice of the profits.

In an email written by Gilliar to Hunter on May 13, 2017, the “Big Guy” was allocated a 10% stake in a lucrative joint venture with Chinese energy conglomerate CEFC.

“10 [percent] held by H[unter] for the Big Guy,” Gilliar wrote.

Three years later, Bobulinski, a Navy veteran, held a press conference to say “there is no question” that the “Big Guy” is Joe Biden.

“Hunter Biden called his dad ‘the Big Guy’ or ‘my Chairman,’ and frequently referenced asking him for his sign-off or advice on various potential deals that we were discussing,” Bobulinski said in October 2020.

Key info for grand jury

Joe was called the “Big Guy” in other emails on Hunter’s laptop or in WhatsApp messages on Bobulinski’s phones. In one case, a Serbian associate of Hunter, Vuk Jeremic, past president of the UN General Assembly, who was on a $330,000 retainer from CEFC, referred to Joe as “Big Man.”

The identity of the “Big Guy” is important enough to form a part of the grand jury investigation in Delaware into Hunter’s business dealings. At least one witness has been asked who the “Big Guy” is.

Hunter’s partners were always careful not to mention Joe’s involvement.

Gilliar warned Bobulinski, in a WhatsApp message on May 20, 2017, about the need for discretion: “Don’t mention Joe being involved, it’s only when u are face to face, I know u know that but they are paranoid.”

Based in the Czech Republic, Gilliar was dubbed “MI6” by Bobulinski, after the British foreign intelligence service, because of Gilliar’s covert manner. He also told Hunter he had worked with British intelligence and introduced a prospective partner in Oman as “former MI Six head of region” in the Middle East. Gilliar wanted to hire the former British “diplomat” David Holtom to help with an Oman energy project they were working on for CEFC.

The MI6 angle is intriguing because another British spy, Christopher Steele, was at the center of the Russia collusion scheme cooked up by Hillary Clinton’s campaign to paint Donald Trump as a Russian agent. Steele was the former head of MI6’s Russia desk.

In a biography on Hunter’s laptop, Gilliar gives his background as “specialist training in Civil / Military security operations and analysis, counter terrorism, close protection and firearms, armed and unarmed combat” with expertise in “security and intelligence-based analytics and systems.”

His first appearance on the laptop is a Feb. 23, 2016, email CC’d to Hunter discussing his upcoming visit to Beijing to meet with the CEFC board and pitch a takeover of US Westinghouse Electric Corporation.

Gilliar would become the driving force behind Hunter and uncle Jim Biden’s multimillion-dollar payments from CEFC.

Through 2015, 2016 and 2017, Gilliar traveled the world, using the Biden name to open doors for CEFC in Oman, Romania, Georgia, Kazakhstan and beyond. Sometimes he was accompanied by Hunter, Jim or another business partner, Rob Walker, a Biden family friend and former Clinton-administration official whose wife, Betsy Massey Walker, was Jill Biden’s assistant when Jill was second lady.

2015 meeting with mogul

The first evidence on the laptop of a meeting between Hunter and CEFC’s billionaire chairman, Ye Jianming, is in late 2015. A meeting with Ye and his associated, CEFC Executive Director Jianjun Zang, was scheduled in Hunter’s diary for Dec. 7, 2015.

“Dinner with CEFC” was in Hunter’s diary on Aug. 11, 2016, at Café Milano in Georgetown, DC, an Italian restaurant where he entertained foreign clients.

Joe went to at least one such Café Milano dinner when he was vice president, on April 16, 2015, when he met with Hunter’s Ukrainian benefactor Pozharskyi, emails on the laptop show. Also invited to the dinner to meet the VP that night was Russian billionaire Yelena ­Baturina.

The national security implications are staggering.

Joe Biden repeatedly has said that he knew “nothing about my son’s overseas business dealings.”

But the laptop is full of evidence to the contrary. The FBI has had possession of the laptop since December 2019, when laptop repair-shop owner John Paul Mac Isaac handed it over.

Now we know why the FBI never investigated the laptop, thanks to whistleblowers who have come forward to Republican Sen. Chuck Grassley alleging a widespread effort within the agency to discredit negative information about the Bidens as Russian disinformation.

Attorney General Merrick Garland was happy to appear this week on NBC to entertain questions about holding Donald Trump to account for Trump’s role in the Jan. 6, 2021, Capitol riot. “We pursue justice without fear or favor,” he said.

Just not when it comes to the Biden family.