Question: Leonora Mary Grosvenor's father was the richest man in Britain in what decade?

Context articles: The Richest Man in Babylon (album)
Hugh Grosvenor, 7th Duke of Westminster
Aban Offshore
Robert Grosvenor, 5th Duke of Westminster
Leonora Anson, Countess of Lichfield
Robin Li
Zong Qinghou
Yukos
Simon Cheong
William Gray (Massachusetts)

The Richest Man in Babylon is the third studio album by Thievery Corporation, it was released in 2002 on their Eighteenth Street Lounge label.
 Like Thievery Corporation's previous albums, "The Richest Man in Babylon" is electronic music with a downtempo aesthetic.
Hugh Richard Louis Grosvenor, 7th Duke of Westminster (born 29 January 1991), styled as Earl Grosvenor until August 2016, is a British aristocrat, billionaire, businessman and landowner.
 He is the third child and only son of Gerald Grosvenor, 6th Duke of Westminster and his wife Natalia Phillips Grosvenor, Duchess of Westminster.
 He inherited the title of Duke of Westminster on 9 August 2016, on the death of his father.
 The duke is estimated to be worth US$13 billion, making him the world's richest person aged under 30.
Aban Offshore (formerly Aban Loyd Chiles Offshore Ltd.) is India's largest offshore drilling services provider to oil companies, mainly for ONGC.
 It is now ventured into international waters as one of its five rigs is doing work for an Iranian oil company.
 The company listed on the Mumbai Stock Exchange Ltd, In 2008, Reji Abraham, managing director of Aban Loyd, was the 605th richest man in the world and the richest man in Kerala, India.
Lieutenant-Colonel Robert George Grosvenor, 5th Duke of Westminster, {'1': ", '2': ", '3': ", '4': "} (24 April 1910 – 19 February 1979) was a British soldier, landowner, businessman and politician.
 In the 1970s he was the richest man in Britain.
Leonora, Countess of Lichfield, LVO (born 1 February 1949) was born as Leonora Mary Grosvenor, a daughter of the 5th Duke of Westminster.
Robin Li or Li Yanhong (; born 17 November 1968) is a Chinese Internet entrepreneur.
 He co-founded the Chinese search engine Baidu and is ranked as the seventh richest man in mainland China with a net worth of US$9.6 billion as of September 2015.
 He is ranked as 119th richest man in the world, according to the Hurun Report Global Rich List 2014.
 In addition, Li also serves as the member of the 12th Chinese People's Political Consultative Conference.
Zong Qinghou (; born 1945) is a Chinese entrepreneur, founder, Chairman and CEO of the Hangzhou Wahaha Group, the leading beverage company in China.
 He was ranked as China's richest man of 2012 and second-richest man of 2013, according to the China Rich List, published by Hurun Report.
 On the Global Rich List, he is 35th richest man in the world, with an estimated net worth of US$20 billion., Zong is a delegate to the Chinese National People's Congress.
OJSC "Yukos Oil Company" (Russian: ОАО Нефтяна́я Компа́ния Ю́КОС , ] ) was an oil and gas company based in Moscow, Russia.
 Yukos was acquired from the Russian government by Russian oligarch Mikhail Khodorkovsky's Bank Menatep during the controversial "loans for shares" auctions of the mid 1990s.
 Between 1996 and 2003 Yukos became one of the biggest and most successful Russian companies, producing 20% of Russia's oil output, as much as Libya or Iraq, and Khodorkovsky became an advocate of democratization, international co-operation and Russian reform.
 In October 2003 Khodorkovsky—by then the richest man in Russia and 16th richest man in the world—was arrested, and the company was forcibly broken up for alleged unpaid taxes shortly after and declared bankrupt in August 2006.
 Courts in several countries later ruled that the real intent was to destroy Yukos and obtain its assets for the government, and act politically against Khodorkovsky.
 In 2014 the largest arbitration award in history, $50 billion (€37,2 billion), was won by Yukos' former owners against Russia.
Simon Cheong () is Singapore's 44th richest man.
 He is the founder of the property developer SC Global Developments Company.
 Cheong was ranked the 22nd richest man in Singapore on Forbes' list in 2008 and has a net worth of US$245 million then.
William Gray (June 27, 1750 (old style; July 8, 1750 new style)– November 4, 1825) was a Massachusetts merchant and politician.
 Born into a lower-class family in Lynn, Massachusetts, he managed to build his own business and rise through the state's political ranks, becoming the richest man in New England, and in the eyes of many the richest man in all of America.
 Prior to the War of 1812, William Gray had the largest private fleet in the United States with 60 square-rigged vessels.