Question: When did the country where Valaichchenai Lagoon is located leave the British Empire?

full_context: Document 1: Sri Lankan independence movement: The Sri Lankan independence movement was a peaceful political movement which aimed at achieving independence and self - rule for Sri Lanka, then Ceylon, from the British Empire. It was initiated around the turn of the 20th century and led mostly by the educated middle class. It succeeded when, on February 4, 1948, Ceylon was granted independence as the Dominion of Ceylon. Dominion status within the British Commonwealth was retained for the next 24 years until May 22, 1972 when it became a republic and was renamed the Republic of Sri Lanka.
Document 2: Dominion of Ceylon: Between 1948 and 1972, Ceylon was an independent country in the Commonwealth of Nations that shared a monarch with Australia, Canada, New Zealand and the United Kingdom, and certain other sovereign states. In 1948, the British Colony of Ceylon was granted independence as Ceylon. In 1972, the country became a republic within the Commonwealth, and its name was changed to Sri Lanka. It was an island country in South Asia, located about 31 kilometres (19.3 mi) off the southern coast of India.
Document 3: History of India: From 1920 leaders such as Mahatma Gandhi began highly popular mass movements to campaign against the British Raj using largely peaceful methods. The Gandhi-led independence movement opposed the British rule using non-violent methods like non-cooperation, civil disobedience and economic resistance. However, revolutionary activities against the British rule took place throughout the Indian subcontinent and some others adopted a militant approach like the Indian National Army that sought to overthrow British rule by armed struggle. The Government of India Act 1935 was a major success in this regard. All these movements succeeded in bringing independence to the new dominions of India and Pakistan on 15 August 1947.
Document 4: Second Sirimavo Bandaranaike cabinet: The Second Sirimavo Bandaranaike cabinet was the central government of Ceylon led by Prime Minister Sirimavo Bandaranaike between 1970 and 1977. It was formed in May 1970 after the parliamentary election and it ended in July 1977 after the opposition's victory in the parliamentary election. The second Sirimavo Bandaranaike cabinet saw Ceylon severing the last colonial ties with Britain as the country became a parliamentary republic in May 1972. The country was also renamed Sri Lanka.
Document 5: Valaichchenai Lagoon: Valaichchenai Lagoon is an estuarine lagoon in Batticaloa District, eastern Sri Lanka. Batticaloa district has three lagoons, such Valaichchenai Lagoon, Batticaloa Lagoon and Vakari Lagoon. Valaichchenai lagoon is situated in populated areas of Valaichchenai, Oddamavadi
Document 6: D. S. Senanayake: Don Stephen Senanayake (; ; 21 October 1883 – 22 March 1952) was a Sri Lankan statesmen. He was the first Prime Minister of Sri Lanka having emerged as the leader of the Sri Lankan independence movement that led to the establishment of self-rule in Sri Lanka. He is considered as the "Father of the Nation".
Document 7: Bar Reef: The Bar Reef is a system of coral reefs just offshore from Sri Lanka's Kalpitiya peninsula. It has the greatest biodiversity of any coral reef in the waters around India and is one of the few pristine coral reef systems in Sri Lanka.
Document 8: British Empire: Britain's remaining colonies in Africa, except for self-governing Southern Rhodesia, were all granted independence by 1968. British withdrawal from the southern and eastern parts of Africa was not a peaceful process. Kenyan independence was preceded by the eight-year Mau Mau Uprising. In Rhodesia, the 1965 Unilateral Declaration of Independence by the white minority resulted in a civil war that lasted until the Lancaster House Agreement of 1979, which set the terms for recognised independence in 1980, as the new nation of Zimbabwe.
Document 9: Valencia: Valencia stands on the banks of the Turia River, located on the eastern coast of the Iberian Peninsula and the western part of the Mediterranean Sea, fronting the Gulf of Valencia. At its founding by the Romans, it stood on a river island in the Turia, 6.4 km (4 mi) from the sea. The Albufera, a freshwater lagoon and estuary about 11 km (7 mi) south of the city, is one of the largest lakes in Spain. The City Council bought the lake from the Crown of Spain for 1,072,980 pesetas in 1911, and today it forms the main portion of the Parc Natural de l'Albufera (Albufera Nature Reserve), with a surface area of 21,120 hectares (52,200 acres). In 1986, because of its cultural, historical, and ecological value, the Generalitat Valenciana declared it a natural park.
Document 10: Shark Valley: Shark Valley is a geological depression at the head of the Shark River Slough in far western Miami-Dade County, Florida, United States. It is currently part of Everglades National Park. Shark Valley empties into Shark River in the Ten Thousand Islands of Monroe County. Shark Valley characteristically includes sawgrass prairie that floods during the rainy season, hence the name "river of grass"—"Pa-Hay-Okee", from the Mikasuki language—for such marshes in the Everglades. Shark Valley features a Visitor Center with educational displays, a park video, an underwater camera and informational brochures. The entrance to Shark Valley is located along Tamiami Trail (US 41) near the Miami-Dade–Collier County line.
Document 11: Zhejiang: Valleys and plains are found along the coastline and rivers. The north of the province lies just south of the Yangtze Delta, and consists of plains around the cities of Hangzhou, Jiaxing, and Huzhou, where the Grand Canal of China enters from the northern border to end at Hangzhou. Another relatively flat area is found along the Qu River around the cities of Quzhou and Jinhua. Major rivers include the Qiangtang and Ou Rivers. Most rivers carve out valleys in the highlands, with plenty of rapids and other features associated with such topography. Well-known lakes include the West Lake of Hangzhou and the South Lake of Jiaxing.
Document 12: Jiquilisco Bay: The Jiquilisco Bay Biosphere Reserve is located on the southeast Pacific coast of El Salvador, in the department of Usulután. Jiquilisco Bay's mangrove-lined inlets and bay hosts the largest abundance of coastal-marine birds in the El Salvador, many of which are threatened or endangered. Over 80 species of migratory birds visit the area to feed on the bay's fish, which include species such as snook, red snapper and corvina. The natural environment of Bahia Jiquilisco has recently led to an increase in eco-tourism in the area.
Document 13: Karachaus Lagoon: Karachaus Lagoon (, ) is a salty lagoon in the Tuzly Lagoons group in Tatarbunary Raion of Odessa Oblast, Ukraine. It was a part of the Alibey Lagoon in past, locating in its south-west part, near the Village of Roylianka. Now it is separated from the Alibey Lagoon by the sandbar. The total area of the lagoon - 7.6 km².
Document 14: Vilsandi: The island of Vilsandi, Saaremaa Parish, Saare County, Estonia is located in the Baltic Sea. It covers an area of some 9 square km and is the westernmost populated island in Estonia. The surrounding waters are shallow and rocky and many ships travelling the Baltic have perished nearby. The island of Vilsandi can be reached by boat, by truck having suitable clearance or on foot by wading from Saaremaa. Much of the island is now part of Vilsandi National Park, which grew from a bird reserve founded in 1910. It is a highly sensitive ecosystem due to the use of the area by many migratory birds as a breeding and nesting ground. Hunting is absolutely prohibited. This park is a popular tourist destination not only for local Estonians, but also people of Finland who are visiting Estonia in greater and greater numbers.
Document 15: S. Mahinda: S. Mahinda arrived in Ceylon (now Sri Lanka) at a young age and was ordained as a Buddhist monk. Having learned the Sinhala language, he became a poet, creating several literary works inspiring patriotism among the Sinhalese and urging them to fight for their freedom during Sri Lankan Independence movement.. He is now considered a national hero of Sri Lanka and one among the greatest of Sinhalese poetry figures of all time.
ground_truth: February 4, 1948
sub_queries: Valaichchenai Lagoon >> country Answer: Sri Lanka
when did Sri Lanka leave the british empire Answer: February 4, 1948