Denning judged in the Court of Appeal at the time, and  held that Sikhs were not a racial or ethnic group.  His ruling was overturned in the House of Lords, notably by Ian Fraser, Baron Fraser of Tullybelton, who outlined seven points by which ethno-religious groups were to be defined. 
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Alfred Denning, Baron Denning: Being
Alfred Denning, Baron Denning was British judge. Explore interesting quotes on being.
                                        
                                        That very day the market manager wrote a letter to Mr. Hook, banning him from trading in the market. 
Ex Parte Hook [1976] 1 WLR 1052 at 1055. 
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                                        Miller v. Jackson [1977] QB 966 at 976. 
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                                        Re Weston's Settlements, [1969] 1 Ch 223. 
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Speech https://api.parliament.uk/historic-hansard/lords/1986/jul/31/european-communities-amendment-bill-1#S5LV0479P0_19860731_HOL_228 in the House of Lords against the Single European Act (31 July 1986)
Speech to Justice, London (28 June 1977), quoted in The Times (29 June 1977), p. 4