DETROIT, MI – MARCH 03: Republican presidential candidate Donald Trump and his wife Melania greet reporters in the spin room following a debate sponsored by Fox News at the Fox Theatre on March 3, 2016 in Detroit, Michigan. Voters in Michigan will go to the polls March 8 for the State’s primary. (Photo by Chip Somodevilla/Getty Images)

Donald Trump’s unfaithfulness to his wife Melania Trump has long been public knowledge. But now the American President’s infidelity is officially in the history books.

Trump’s former lawyer Michael Cohen testified to the US Congress on Wednesday, after pleading guilty to lying to investigators in Robert Mueller’s Russia probe, which is looking into Russian involvement in the 2016 election.

In his explosive testimony, Cohen described Trump as “a racist,” “a con man” and “a cheat.” He also revealed that Mr Trump continued to be involved in plans to build a Trump Tower in Moscow throughout his 2016 presidential campaign, something Trump has repeatedly denied.

WASHINGTON, DC – FEBRUARY 27: Michael Cohen, former attorney and fixer for President Donald Trump is sworn in before testifying before the House Oversight Committee on Capitol Hill February 27, 2019 in Washington, DC. Last year Cohen was sentenced to three years in prison and ordered to pay a $50,000 fine for tax evasion, making false statements to a financial institution, unlawful excessive campaign contributions and lying to Congress as part of special counsel Robert Mueller’s investigation into Russian meddling in the 2016 presidential elections. (Photo by Chip Somodevilla/Getty Images)

But taking centre stage is President Trump’s affair with adult film star Stormy Daniels, real name Stephanie Clifford.

Cohen admitted to paying $130,000 to Daniels at the direction of Mr Trump, just days before the 2016 election, to silence Clifford from speaking out about her months-long affair with the President, which began in 2006.

Cohen provided the Congress with cheques signed by the President himself. It’s particularly incriminating evidence for the President, especially since he has previously claimed to have no knowledge of the payments to Clifford.

In an extraordinary scene, Cohen made a public apology to Melania Trump for lying to her about her husband’s extra-marital affairs and the cheques made to Clifford.

NEW YORK – SEPTEMBER 15: Donald Trump and Melania Trump attend the Michael Kors Spring 2011 fashion show during Mercedes-Benz Fashion Week at The Theater at Lincoln Center on September 15, 2010 in New York City. (Photo by Michael Loccisano/Getty Images for IMG)

“He [Trump] asked me to pay off an adult film star with whom he had an affair and to lie to his wife about it, which I did,” Cohen told a packed congress, which included Democratic senator Alexandria Ocasio-Cortez.

“Lying to the First Lady is one of my biggest regrets. She is a kind, good person.

“I respect her greatly and she did not deserve that.”

Coincidentally – or perhaps not – Melania Trump is not with the President right now as he attends a summit with North Korean leader Kim Jong Un in Hanoi Vietnam.

NEW YORK, NY – APRIL 16: (L to R) Adult film actress Stormy Daniels (Stephanie Clifford) and Michael Avenatti, attorney for Stormy Daniels, speak to the media as they exit the United States District Court Southern District of New York for a hearing related to Michael Cohen, President Trump’s longtime personal attorney and confidante, April 16, 2018 in New York City. Cohen and lawyers representing President Trump are asking the court to block Justice Department officials from reading documents and materials related to Cohen’s relationship with President Trump that they believe should be protected by attorney-client privilege. Officials with the FBI, armed with a search warrant, raided Cohen’s office and two private residences last week. (Photo by Drew Angerer/Getty Images)

It’s unusual for the First Lady not to join the President on an overseas trip unless there’s a specific reason.

A spokesperson for Mrs Trump confirmed she was not attending the Vietnam summit, but did not say why.

WEST PALM BEACH, FL – MARCH 17: President Donald Trump, his wife Melania Trump and their son Barron Trump arrive together on Air Force One at the Palm Beach International Airport to spend part of the weekend at Mar-a-Lago resort on March 17, 2017 in West Palm Beach, Florida. President Trump has made numerous trips to his Florida home since the inauguration. (Photo by Joe Raedle/Getty Images)

While Melania did not attend Trump’s last summit with Kim Jong Un in Singapore in June 2018, the reason given was that she was recovering after being treated for a benign kidney condition.

So it’s odd that the First Lady would not be by the President’s side for the Vietnam summit, such a crucial and historic event, and give no reason for her absence.

Melania has been forced to endure the shame of her husband’s infidelities being broadcast to the public since he became America’s president. But perhaps the thought of standing by Trump’s side at the Vietnam summit, smiling and waving while her husband’s cheating was being recorded in the United States history books, was just too much of an indignity to bear.