Largescale evacuation from Gibraltar to the UK occurred during World War II, Gibraltar's location in a war-torn nation meant mass evacuation from the territory was inevitable. Approximately 16,700 evacuees left Gibraltar with the UK taking in 12,500 of them, the majority settled in Kensington, Fulham and Barking (all London), although numerous others sought refuge elsewhere in the country (particularly Northern Ireland). Due to lack of accommodation, many of these Gibraltarians were reluctant to stay in the UK, and many eventually returned to Gibraltar after stability became better established.
According to the 2001 UK Census, 11,830 people born in Gibraltar were residing in the UK, which constitutes the largest group of British overseas territory citizens residing in mainland UK. The UK is also the country with the largest group of Gibraltarians resident outside Gibraltar.