Construction is underway on a 77,000-square-foot Bel Air mansion attached to billionaire Trump chum Thomas Barrack Jr., who filed plans for the project in 2014. But the Colony Capital CEO is not building it for himself, sources told The Real Deal.

The major investor behind the Peter Marino-designed project is the Al Thani royal family of Qatar, the sources said.

“Barrack is just the frontman,” said a source familiar with the project. “It’s got to cost at least $100 million, probably more.”

The site — which spans eight acres of land right above the Bel Air Country Club at 11101 Chalon Road — was purchased in 2010 for $35 million, property records show. It’s unclear who owns the land. A representative of Barrack Jr. could not be reached for comment.

Barrack Jr. has deep ties with investors in the Middle East, including the Al Thani family. In 2011, Barrack Jr. worked with the Qatar Investment Authority, the sovereign wealth fund overseen by the royal family, to purchase Miramax Films and some of its assets for $660 million.

In 2015, the Arabic-speaking billionaire intervened on behalf of the family in a dispute over the ownership of the Claridge’s Hotel in London. In a bidding war with Daily Telegraph owners David and Frederick Barclay, Barrack swooped in to purchase $82 million of debt on the property, which Sheikh Hamad bin Khalifa Al Thani, the former emir of Qatar, acquired with his son, Jassim bin Hamad, for $2.4 billion.

The Al Thanis are no strangers to L.A. Another one of Sheikh Hamad bin Khalifa Al Thani’s sons (he has 24 children with three wives) made headlines when he was filmed drag racing his bright yellow Ferrari in the streets of Beverly Hills. He subsequently fled the country, telling the police that he has diplomatic immunity.