I heard lots of these, but only saw 4 or 5.
Richmond Park, London, Feb 2009
(Feral population in London)
Locally, they are called "kingston parakeets".
The Rose-ringed Parakeet (Psittacula krameri), also known as the Ring-necked Parakeet, is a gregarious tropical Afro-Asian parakeet species that has an extremely large range. Since the trend of the population appears to be increasing, the species was evaluated as Least Concern by IUCN in 2012.