Update (23 September 5pm GMT): The petition to save Uber has now attracted more than 560,000 signatures.
Change.org have said this makes it "the fastest growing petition we've seen in the UK this year," the BBC reports.
“I know that Uber has become a popular service for many Londoners – but it would be wrong for TfL to license Uber if there was any way this could pose a threat to Londoners’ safety or security," the Mayor said.
"I have every sympathy with Uber drivers and customers affected by this decision but their anger really should be directed at Uber. They have let down their drivers and customers by failing, in the view of TfL, to act as a fit and proper operator."
Original story: If you live in or around London, or visit the capital from time to time, you'll almost certainly have had a conversation about Uber in the last 24 hours. On Friday morning, Transport for London (TfL) announced that it has refused to renew Uber's licence, arguing that the company isn't "fit and proper" to hold a private operator licence due to numerous concerns over security and public safety.
The reaction on Twitter has been heated because it's difficult to know exactly what to think about TfL's decision. Writing for Refinery29, Marie-Claire Chappet expressed a view that many of us will be able relate to, at least broadly. "I have no deep love for Uber as a company. I know that it does not have a moral high ground or a clean slate. I know I am lucky to have only had safe and positive experiences in the back of their cars. But what so many of us are pre-emptively mourning is a post-Uber London," she wrote.
"How can we, as Londoners, stand to pay £40 on a journey that we know we once got for £14? What options are there for women in London without an inexhaustible disposable income - women who feel threatened by night buses and tubes and unlicensed mini cabs?"
Following Friday's announcement, a Change.org petition titled "Save Your Uber in London" was set up. "If this decision stands, it will put more than 40,000 licensed drivers out of work and deprive millions of Londoners of a convenient and affordable form of transport," the petition argues. "This decision is affecting the real lives of a huge number of honest and hard-working drivers in London."
At the time of writing, the petition - which will be delivered to the Mayor of London, Sadiq Khan - has attracted more than 475,000 signatures. And unsurprisingly, it's prompting a range of conflicting reactions on Twitter.
Uber has already said it will appeal Tfl's decision, citing the "3.5 million Londoners who use our app, and more than 40,000 licensed drivers who rely on Uber to make a living." The company now has 20 days to prepare and formally lodge its appeal.