The U.K.’s Information Commissioner is starting off the week with a GDPR bang: This morning, it announced that it has fined British Airways and its parent International Airlines Group (IAG) £183.39 million ($230 million) in connection with a data breach that took place last year that affected a whopping 500,000 customers browsing and booking tickets online. In an investigation, the ICO said that it found “that a variety of information was compromised by poor security arrangements at [BA], including log in, payment card, and travel booking details as well name and address information.”

The fine — 1.5% of BA’s total revenues for the year that ended December 31, 2018 — is the highest-ever that the ICO has leveled at a company over a data breach (previous “record holder” Facebook was fined a mere £500,000 last year by comparison).

And it is significant for another reason: It shows that data breaches can be not just a public relations liability, destroying consumer trust in the organization, but a financial liability, too. IAG is currently seeing volatile trading in London, with shares down 1.5% at the moment.

In a statement to the market, the two leaders of IAG defended the company and said that its own investigations found that no evidence of fraudulent activity was found on accounts linked to the theft (although as you may know, data from breaches may not always be used in the place where it’s been stolen).

“We are surprised and disappointed in this initial finding from the ICO,” said Alex Cruz, British Airways chairman and chief executive. “British Airways responded quickly to a criminal act to steal customers’ data. We have found no evidence of fraud/fraudulent activity on accounts linked to the theft. We apologise to our customers for any inconvenience this event caused.”

Willie Walsh, International Airlines Group chief executive, added in his own comment that “British Airways will be making representations to the ICO in relation to the proposed fine. We intend to take all appropriate steps to defend the airline’s position vigorously, including making any necessary appeals.”

The degree to which companies are going to be held accountable for these kinds of breaches is going to be a lot more transparent going forward: The ICO’s announcement is part of a new directive to disclose the details of its fines and investigations to the public.

“People’s personal data is just that – personal,” said Information Commissioner Elizabeth Denham in a statement. “When an organisation fails to protect it from loss, damage or theft it is more than an inconvenience. That’s why the law is clear – when you are entrusted with personal data you must look after it. Those that don’t will face scrutiny from my office to check they have taken appropriate steps to protect fundamental privacy rights.”

The ICO said in a statement this morning that the fine is related to infringements of the General Data Protection Regulation (GDPR), which went into effect last year prior to the breach. More specifically, the incident involved malware on BA.com that diverted user traffic to a fraudulent site, where customer details were subsequently harvested by the malicious hackers.

BA notified the ICO of the incident in September, but the breach was believed to have first started in June. Since then, the ICO said that British Airways “has cooperated with the ICO investigation and has made improvements to its security arrangements since these events came to light.” But it should be pointed out that even before this breach, there were other examples of the company treating data protection lightly. (Now, it seems BA has learned its lesson the hard way.)

From the statement issued by IAG today, it sounds like BA will choose to try to appeal the fine and overall ruling.

While there are a lot of question marks over how the U.K. will interface with the rest of Europe over regulatory cases such as this one after it leaves the EU, for now it’s working in concert with the bigger group.

The ICO says it has been “lead supervisory authority on behalf of other EU Member State data protection authorities” in this case, liaising with other regulators in the process. This also means that these authorities where its residents were also affected by the breach will also have a chance to provide input on the ruling before it is completely final.