And within around half an hour, nearly half a million people had already downloaded the game on Android phones and before the end of the day had shot to the top of the app stores.
The hit game from the 90s has been reincarnated as a mobile game app for the 21st century and people can't get enough of it.
Now, a week after first launching in the US, Australia and New Zealand, it's become available in the UK on Google's Play Store - where the number of downloads are displayed - and the Apple app store. The game also launched in Germany on Wednesday.
Thousands of people in the UK have already been using it by doing a workaround on their phones, but anyone who can't be bothered with the faff can now get it simply and easily.
According to SimilarWeb, which has already pegged the app as more popular than Tinder in the US - and soon to overtake Twitter - Pokemon Go has already been installed on more than three per cent of all Android phones in the UK.
The game has taken off like nothing before, among young and old (no doubt as much about nostalgia as the game itself), with Pokemon being spotted everywhere from Downing Street to Tube train tracks.
“The success of Pokémon Go has been absolutely staggering," said Nicolas Beraudo Europe managing director od app analytics firm App Annie.
"Since its release in the US and Australia, it has topped the free-to-download charts and has already generated millions in revenue for Niantic."
App Annie said it has already shot to the top of the UK app charts, and it expects it to dominate for several months and is already making $1m a day in net revenue.
"If Niantic Labs gives the game a worldwide presence, fixes the server issues and adds more social and PvP features, we can easily envision it making a $1bn a year," said Beraudo.
The appearance of Pokemon - seen via augmented reality on the phone screen - in surprise places had led to one children's charity calling on the game's makers, Nintendo and Niantic, to delay its launch in the UK. The NSPCC raised concerns that the game did not adequately protect children.
Pokemon Go has gone down just as well with investors as players; Nintendo's share price has risen more than 50 per cent in the last week on the back of the game's success.
According to EE, even before today's launch, 350,000 people on the network were playing the game yesterday.
"This is the fastest take up of an app or game we've ever seen - and that's before it's officially launched! People across the country are going to be relying on a mobile data network that's everywhere they go."
The good news for anyone who has already downloaded the app via unofficial methods, is that users are reporting that they can install the official app and their progress through the game will be saved.
Here's how people are reacting to the launch...
If you want time off from the Britocalypse then the good news is Pokemon Go is finally in the UK app store 👍 👍 👍— The Poke (@ThePoke) July 14, 2016