Question: When did the world's seventh largest bank buy Antony Gibbs & Sons?

Context paragraphs:
Antony Gibbs &amp; Sons: Antony Gibbs & Sons was a British trading company, established in London in 1802, whose interests spanned trading in cloth, guano, wine and fruit, and led to it becoming involved in banking, shipping and insurance.  Having been family-owned via a partnership from its foundation, by the turn of the 20th century it was focused on banking and insurance.  Floated on the London Stock Exchange in 1973, it was bought by HSBC in 1981 and formed the basis of its insurance broking arm, now part of global insurance company Marsh & McLennan.

SpareBank 1 SR-Bank: SpareBank 1 SR-Bank (), formerly Sparebanken Rogaland, is the largest savings bank in Norway.  The bank has 50 branch offices in 26 municipalities in Rogaland, Agder and Hordaland and a head office in Stavanger.  It has 250,000 private and 40,000 institutional customers with total assets of NOK 67 billion.  The bank is a founding member of the bank alliance SpareBank 1 and is Norway's seventh largest bank.

Baron Aldenham: Baron Aldenham, of Aldenham in the County of Hertford, is a title in the Peerage of the United Kingdom that was created on 31 January 1896 for the businessman Hucks Gibbs.  He was head of the family firm of Antony Gibbs & Sons (founded by his grandfather Antony Gibbs) and a director and Governor of the Bank of England.  Gibbs also briefly sat as a Conservative Member of Parliament for the City of London.  His fourth son Herbert Cokayne Gibbs was created Baron Hunsdon of Hunsdon in 1923 (see below).  Lord Aldenham was succeeded by his eldest son, the second Baron.  He also represented the City of London in the House of Commons as a Conservative.  He was succeeded by his son, the third Baron.  On the latter's death in 1939 the barony of Aldenham was inherited by his cousin the second Baron Hunsdon of Hunsdon (see the Baron Hunsdon of Hunsdon for earlier history of this title).  He served as chairman of Antony Gibbs & Sons.  s of 2017 the titles are held by his grandson, the sixth Baron, who succeeded his father in 1986.

Bank of the Philippine Islands: Bank of the Philippine Islands (Filipino: "Bangko ng Kapuluang Pilipinas" , Spanish: "Banco de las Islas Filipinas" , commonly known as BPI; ) is the oldest bank in the Philippines still in operation and is the country's fourth largest bank in terms of assets, the country's second largest bank in terms of market capitalization, and the country's most profitable bank.  It is owned by the Ayala Corporation, the largest conglomerate in the Philippines, and is based in Makati's Central Business District, on the corner of Ayala Avenue and Paseo de Roxas.  As of 2014, it is currently listed in Forbes as the Philippines' largest bank in terms of market value and overall ranking.

Raiffeisen Bank Aval: Raiffeisen Bank Aval is a commercial bank based in Kiev, Ukraine.  It was registered on March 27, 1992, and is the seventh largest bank in the country.  It operates more than 600 branches across the country and offers retail banking services to individuals and organisations.  The bank has been a subsidiary of Austrian Raiffeisen Bank International since 2006.

William Gibbs (businessman): William Gibbs (1790–1875) was an English businessman, best known as one of three founding partners in Antony Gibbs & Sons, a religious philanthropist, and the owner who developed Tyntesfield in Wraxall, North Somerset.

Antony Gibbs: Antony Gibbs (17 October 1925 – 26 February 2016) was a British film and television editor with more than 40 feature film credits.

HSBC: HSBC Holdings PLC is a British multinational banking and financial services holding company, tracing its origin to a hong in Hong Kong.  It is the world's seventh largest bank by total assets and the largest in Europe with total assets of US$2.374 trillion (as of December 2016).  It was established in its present form in London in 1991 by The Hongkong and Shanghai Banking Corporation Limited to act as a new group holding company.  The origins of the bank lie mainly in Hong Kong and to a lesser extent in Shanghai, where branches were first opened in 1865.  The HSBC name is derived from the initials of the Hongkong and Shanghai Banking Corporation.  The company was first formally incorporated in 1866.  The company continues to see both the United Kingdom and Hong Kong as its "home markets".

Union Bank of Switzerland: Union Bank of Switzerland (UBS) was a large integrated financial services company located in Switzerland.  The bank, which at the time was the second largest bank in Switzerland, merged with Swiss Bank Corporation in 1998, to become UBS to form what was then the largest bank in Europe and the second largest bank in the World.

HSBC Bank Canada: HSBC Bank Canada, formerly the Hongkong Bank of Canada (French: "Banque HSBC Canada" ), is a bank in Canada that is part of British banking giant HSBC - one of the largest banking groups in the world.  HSBC Canada is the seventh largest bank in Canada, with offices in every province except Prince Edward Island, and is the largest foreign-owned bank in the country.  Corporate headquarters are in the financial district of Vancouver, British Columbia.  HSBC Bank Canada's Institution Number (or bank number) is 016.

Supporting paragraphs: Antony Gibbs &amp; Sons HSBC
Answer: 1981