The parakeets you see in London are ring-necked parakeets (Psittacula krameri), also known as roseringed parakeets. They are native to Asia and sub-Saharan Africa, but they have become well-established in London and other parts of the UK.
The most popular theory is that these parakeets were originally kept as pets and either escaped or were released into the wild. Their adaptability to the local climate and their ability to thrive in urban environments have allowed their population to grow significantly. There are also various urban legends, such as the birds escaping from the set of the 1951 film “The African Queen” or being released by Jimi Hendrix, but these stories are not supported by evidence.
Today, you can spot these colorful birds in many parks and gardens across London, adding a touch of exotic flair to the city’s landscape.