Question: Egg Banking is the former bank that now trades as what third-largest building society?

Context paragraphs:
Marble Rock Bank: Marble Rock Bank, also known as the Marble Rock Historical Society Building, is a historic building located in Marble Rock, Iowa, United States.  New York native J.B. Shepardson settled in Marble Rock in 1864.  He was involved in a number of ventures including running a store, a hotel, and land speculation.  He and his brother S.E. Shepardson opened the Marble Rock Bank in 1873, and they had this building constructed in 1885.  It is a single-story structure that features a stone facade, nine corbels that support a plain cornice, and a simple stone plaque that identified the building as a bank.  The building survived two fires that destroyed much of the town in 1899, making this the oldest commercial building in town.  Banking operations moved from here in 1927, and the bank itself closed in 1932.  The Marble Rock Historical Society, established in 1972, bought the building in 1974 for use as a museum.  They have subsequently acquired other buildings that have been added to the museum complex.  The former bank building was listed on the National Register of Historic Places in 1982.

Kent Reliance: Kent Reliance, formerly known as Kent Reliance Building Society and also known as KRBS, is a banking services provider based in Kent, England.  Until 31 January 2011 KRBS stood for Kent Reliance Building Society, which was created in 1986 and incorporated Chatham Reliance (established 1898), Dover District (established 1861), Herne Bay (established 1888) and Kent and Canterbury (established 1847).  On 1 February 2011, Kent Reliance Building Society transferred its business to a new bank, OneSavings Bank plc (which trades as Kent Reliance).

The Cambridge Building Society: The Cambridge Building Society is a UK mutual building society based in Cambridge, Cambridgeshire, England.  It is the 14th largest in the United Kingdom based on total assets of £1,128 million at 31 December 2015.  It is a member of the Building Societies Association.  The Society was formed in 1850 as the Cambridgeshire Permanent Benefit Building Society, adopting its current name in 1945.  There is no connection between this Society and the Cambridge Foresters’ Benefit Building Society which was dissolved in 1960 or the Cambridge Peers Economic Building Society which was dissolved in 1972.

Capital Bank Financial: Capital Bank Financial Corp. (, previously called North American Financial Holdings Inc., or NAFH) is a bank holding company headquartered in Coral Gables, Florida with $10 billion in assets as of first quarter 2017 and 193 branches.  Former Bank of America vice chairman Gene Taylor is chief executive, former Bank of America executive and Fifth Third Bank CFO, Chris Marshall is CFO and former Bank of America executive, R. Bruce Singletary is Chief Risk Officer.  Former Morgan Stanley research analyst, Kenneth Posner, manages research.  Its original purpose was to take over banks that had difficulties due to the financial crisis of 2007–2010, making money by paying low prices and then improving the banks' performance.  The company's main interest was banks in the Carolinas and Florida, but in 2011, NAFH moved into Tennessee and Virginia for the first time.  Despite buying seven distressed, money losing banks, Capital Bank has been profitable since inception and has consistently posted improved returns for each of its five years of operations.  Capital Bank completed a successful IPO in September 2012 and now trades on the NASDAQ under the ticker CBF.  Capital Bank stock has done well since its debut, outperforming most bank indexes over the past few years.

Portman Building Society: The Portman Building Society was a mutual building society in the United Kingdom, providing mortgages and savings accounts to consumers and offering loans to commercial enterprises.  Its head office was in Bournemouth and its administration centre in Wolverhampton.  Portman merged with the Nationwide Building Society in August 2007, at which time it was the third largest building society in the UK and the largest regional building society in the south of England, with 154 branches and assets exceeding £15 billion.

Egg Banking: Egg is a former British internet bank headquartered in Derby, that is now a trading name of Yorkshire Building Society.  Egg was born out of the UK banking arm of Prudential plc, Prudential Banking plc, which was established in 1996, and the Egg brand was launched in 1998.  The first online credit card was launched in 1999.

Yorkshire Building Society: The Yorkshire Building Society is the third largest building society in the UK, with its headquarters in Bradford, West Yorkshire, England.  It is a member of the Building Societies Association.

Northern Rock: Northern Rock, formerly the Northern Rock Building Society, was a British bank.  Based at Regent Centre in Newcastle upon Tyne, United Kingdom, Northern Rock was originally a building society.  It demututalised and became Northern Rock bank in 1997, when it floated on the London Stock Exchange with the ticker symbol NRK.  During the early 2000s the company borrowed substantially to fund mortgages, with the aim of ambitious growth, and also donated large amounts to charitable purposes and communities directly and through sponsorships.  The global banking crisis beginning around 2007–2008 meant that it was unable to produce income as expected from its loans, and was at risk of being unable to repay the amounts it had borrowed.  The news that the bank had approached the government for support with its liquidity led within 24 hours to a public lack of confidence and concerns that savings were at risk, and the bank failed following a bank run as people rushed to withdraw their savings.  It was the first British bank in 150 years to fail due to a bank run.

Building society: A building society is a financial institution owned by its members as a mutual organization.  Building societies offer banking and related financial services, especially savings and mortgage lending.  Building societies exist in the United Kingdom (UK), and used to exist in Ireland and several Commonwealth countries.  They are similar to credit unions in organisation, though few enforce a common bond.  However, rather than promoting thrift and offering unsecured and business loans, the purpose of a building society is to provide home mortgages to members.  Borrowers and depositors are society members, setting policy and appointing directors on a one-member, one-vote basis.  Building societies often provide other retail banking services, such as current accounts, credit cards and personal loans.  The term "building society" first arose in the 18th century in Great Britain from cooperative savings groups.

Adelaide Bank: The Adelaide Bank was a publicly listed bank with its head office in Adelaide, South Australia (and should not be confused with the Bank of Adelaide which fell into financial difficulty in the 1970s and was taken over by the ANZ Bank).  It was established on 1 January 1994 from the Co-operative Building Society of South Australia Limited, which was Australia's largest building society as a result of a merger with the Hindmarsh Building Society.  On 9 August 2007 it merged with the Bendigo Bank, (), and Adelaide Bank shares are no-longer quoted on the ASX.  Since 2008 the new entity has been known as the Bendigo and Adelaide Bank.

Supporting paragraphs: Egg Banking Yorkshire Building Society
Answer: Yorkshire Building Society