“While Uber has revolutionized the way people move in cities around the world, it’s equally true that we’ve gotten things wrong along the way,” Khosrowshahi writes. “On behalf of everyone at Uber globally, I apologize for the mistakes we’ve made.”

In his message, Khosrowshahi promises to appeal the TfL decision but says Uber plans to do so “with the knowledge that we must also change.”

“As Uber’s new CEO, it is my job to help Uber write its next chapter,” he writes. “We won’t be perfect, but we will listen to you; we will look to be long-term partners with the cities we serve; and we will run our business with humility, integrity and passion.”

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The letter’s admission of mistakes made is a stark departure from the defiant approach of former chief executive Travis Kalanick, whom Khosrowshahi replaced last month, and is perhaps one of the first indications of how Khosrowshahi plans to approach his new gig.

In announcing its ban on Friday, TfL, the authority that regulates London’s taxis, said it had determined that the company “is not fit and proper to hold a private hire operator license.” In its damning finding, TfL cited Uber’s inadequate screening and background checks of drivers, its “approach to how medical certificates are obtained,” and the use of its controversial “Greyball” software that blocks regulators from gaining full access to the app. The TfL also questioned Uber’s “approach to reporting serious criminal offenses” by its drivers—an issue raised in an extensive submission by the Metropolitan Police.

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Uber on Friday launched an online petition asking London Mayor Sadiq Khan to reverse the TfL’s decision. By Monday morning, it had garnered more than 750,000 signatures.

Khan indicated Monday that he wasn’t impressed by Uber’s first response to the news on Friday, which drew on the company’s more aggressive tactics of the past. It had immediately threatened legal action against TfL and launched a new PR campaign to raise public support for it. U.K. general manager Tom Elvidge said the decision sent a message that “London is far from being open and is closed to innovative companies.”

“I appreciate Uber has an army of PR experts. I appreciate Uber has an army of lawyers. They’ve also made aggressive threats about taking us to court and all the rest of it,” Khan told the BBC’s flagship radio news program Today. “You can’t have it both ways – on the one hand acting in an aggressive manner and threatening all sorts of things, on the other hand briefing to journalists that they want to do a deal with TfL.”