The vast business empire upon which Donald Trump made his name is on the line in a civil fraud trial that began on Monday in New York.

The former president, his two adult sons and the wider Trump Organization are accused of massively inflating the value of their properties by over $2bn (£1.65bn), in order to secure favourable loans.

On the trial's first day, Mr Trump made a surprise appearance at the courthouse where he lambasted the judge and the New York attorney general who brought the case.

He has denied any wrongdoing, calling the case a sham.

Here are five things to know about the trial.

A defeat would mark a significant blow to the real estate empire that propelled him to national recognition long before he ran for the White House.

Those holdings constitute a significant chunk of his personal fortune and self-image. Earlier this year, Forbes Magazine estimated that his New York properties alone are worth $720m of his estimated $2.5bn.

Mr Trump has repeatedly pointed to his achievements in the New York real estate market as a source of personal pride.

In a 2015 interview with Bella NYC magazine, for example, Mr Trump touted the "many great buildings" that he has built and owns as his greatest accomplishment outside of his family.

A victory for prosecutors would mean that Mr Trump and his company would have to pay a $250m fine and be banned from doing business in New York, prising Trump Tower and the rest of his holdings from his grasp.

His presence in court suggests that he knows how high the stakes are.

Two of Mr Trump's adult children - Donald Jr and Eric - are co-defendants in the case and on the list of witnesses. The two took over the management of the Trump Organization in 2017, the year their father became president.

Like their father, both of Mr Trump's sons are accused of what Attorney General Letitia James has described as "persistent and repeated fraud" regarding their business.

The lawsuit filed by Ms James cites multiple specific allegations against both Eric and Donald Jr, largely pertaining to allegedly fraudulent assessments of value of real estate properties.

The lawsuit seeks to bar both men from serving as an officer or director in "any New York corporation or similar business entity" registered or licensed in the state.

Mr Trump's defence team plans to call 128 witnesses, including the former president, his two sons and his daughter Ivanka. His former lawyer Michael Cohen will testify for the prosecution.

Last week, the judge in the case, Arthur Engoron, ruled that Mr Trump misrepresented his wealth by millions of dollars.

His Mar-a-Lago estate in Florida was over-valued by 2,300% in one financial statement and his Trump Tower triplex was presented as three times its actual size, the ruling said.

The judge ordered that some of Mr Trump's companies be removed from his control. While the scope of this ruling is still unclear, it could mean that the Trump Organization could be forced to hand over control to a court-appointed receiver, or ultimately have to sell some of its most iconic landmarks.

The upcoming trial will focus on six other claims made in the lawsuit, including falsification of business records, insurance fraud and conspiracy.

On the opening day, lead attorney for the state, Kevin Wallace, said the defendants falsified records for personal gain. They knew the statements were false, he said, and "then used them to pursue and obtain financial benefits".

The upcoming trial is a bench trial, meaning that the ultimate decision on whether the co-defendants are liable and any damages or penalties rest on Judge Engoron alone.

While Mr Trump has pointed to a lack of jury as evidence that the trial is unfair, Mr Engoron said on Monday that his team never asked for a jury.

Judge Engoron and Ms James - both Democrats - have already sparred with Mr Trump and his legal team.

In April 2022, for example, Judge Engoron held Mr Trump in contempt for refusing to turn over documents related to the case, and rejected attempts by Mr Trump's lawyers to delay the start of the trial.

The former president has called them both "deranged" and in Ms James' case, a "racist" who is conducting a politically-motivated witch hunt.

This civil case is one of several ongoing legal battles the current Republican presidential frontrunner is facing.

He is also facing three criminal indictments.

Two relate to his alleged efforts to overturn the results of the 2020 presidential election and another to false accounting over hush money.

A fourth case sees Mr Trump facing 40 criminal charges over his alleged mishandling of classified material after he left the White House.

Altogether, Mr Trump is facing 91 felony charges, including 44 federal ones and 47 state charges. He denies all the charges.