"This legal action is very much a last resort. We're particularly disappointed that, after a lengthy consultation process with Transport for London, the goalposts have moved at the last minute and new rules are now being introduced that will be bad for both drivers and tech companies like Uber," General Manager of Uber London Tom Elvidge said in a statement.

Uber has taken particular issue with a new English language test any driver originating from a primarily non-English-speaking country will have to pass in order to apply for or renew a private hire licence. The updated regulations provided for a demonstration of "a certain standard of English," but as it has turned out, this means passing a two-hour, B1-level exam complete with essay questions. Uber argues this goes way beyond what is necessary and will impact the number of private hire drivers on the road, who already have to go through a "rigorous and costly process" to obtain a licence. According to the ride-hailing service, this requirement contravenes the Equality Act.

TfL, however, believes it's necessary for drivers to have a level of English that allows them to discuss fares, routes and safety information, as well as be able to read and understand material the authority sends their way.

The new measures require every private hire driver to have year-round commercial insurance. TfL says this is to guarantee drivers have the appropriate insurance in place whenever they are using their vehicle for work. Uber contends this is unfair to seasonal and part-time drivers who fit shifts in when they can -- the expense of year-round insurance leaving them out of pocket or putting them off driving altogether.

Uber also isn't happy with having to notify TfL before making changes to its "operating model." For the ride-hailing outfit, this means it can't add new services or features to its app without running them by the authority first. TfL says this is to ensure changes don't diminish passenger safety and meet legislative requirements, while Uber claims it stifles innovation.

Though Uber allows users to call and message drivers, as well as seek additional support through its app, new guidance states passengers must be able to talk to someone other than the driver based in a call centre in London. Uber isn't keen on the idea of establishing a round-the-clock call centre in the capital to meet these requirements, also arguing black cabs aren't subject to any such rule. TfL, however, considers centralised support "an important safety requirement."

In response to Uber's belief the rules are unlawful, a TfL spokesperson said the authority "will be robustly defending the legal proceedings brought by them in relation to the changes to private hire regulations. These have been introduced to enhance public safety when using private hire services and we are determined to create a vibrant taxi and private hire market with space for all providers to flourish."

It's now up to the courts to decide, of course, but Addison Lee has already made it clear that Uber doesn't speak on behalf of the entire private hire industry. When Uber began its lobbying efforts last week, the CEO of Addy Lee penned a letter to London Mayor Sadiq Khan saying his company fully supported the updated regulations. He also indirectly accused Uber of attempting to "water down" the rules, specifically the commercial insurance requirements.

Being both a more traditional and high-end private hire service, though, it's likely Addison Lee already has internal English language and insurance requirements that mean the regulations are of no consequence to them. Whether all private hire operators feel the same is a different matter.