Question: Mary Soames' mother was born on what date?

full_context: Document 1: Anne Chamberlain: Anne de Vere Chamberlain (née Cole; 1883 – 12 February 1967) was the wife of British Prime Minister Neville Chamberlain.
Document 2: Montagu Porch: Montagu Phippen Porch (1877- November 1964) was Winston Churchill's stepfather, although three years his junior. He was born in 1877 in Glastonbury, a parish of Somerset in the United Kingdom. He was educated at Magdalene College in Cambridge. In 1900 he joined the Imperial Yeomanry, which was a Cavalry regiment of the British Army. In 1906 he joined the Colonial Service and served as an officer until 1919, with the majority of his duties served in Africa. On June 1, 1918, Porch married Lady Randolph Churchill, mother of Winston Churchill. There was quite an age difference here as Porch was 42 and Lady Randolph Churchill (Jennie Jerome) was 64. It was Lady Randolph's third marriage and the first for the younger Porch. The couple remained married for three years until Lady Randolph Churchill's death in 1921.
Document 3: Mary Soames: Mary Soames, Baroness Soames, ("née" Spencer-Churchill; 15 September 1922 – 31 May 2014) was the youngest of the five children of Winston Churchill and his wife, Clementine. She was the wife of Christopher Soames.
Document 4: Winston Churchill: Sir Winston Leonard Spencer-Churchill, {'1': ", '2': ", '3': ", '4': "} (30 November 187424 January 1965) was a British statesman, army officer, and writer. He served as Prime Minister of the United Kingdom from 1940 to 1945 and again from 1951 to 1955. As a Member of Parliament (MP), he represented five constituencies over the course of his career. As Prime Minister, Churchill led Britain to victory during World War II. He led the Conservative Party for fifteen years from 1940 to 1955.
Document 5: Winston Churchill (Cavalier): Sir Winston Churchill, FRS (18 April 1620 – 26 March 1688), known as the "Cavalier Colonel", was a British soldier, nobleman, historian, and politician. He was the father of John Churchill, 1st Duke of Marlborough, as well as an ancestor of his 20th-century namesake, Prime Minister Sir Winston Churchill.
Document 6: Later life of Winston Churchill: The later life of Winston Churchill documents the life of the British statesman from the end of World War II and his second term as Prime Minister of the United Kingdom, until his subsequent death and funeral in 1965. After the end of the war Churchill had to step down as Prime Minister of the United Kingdom because the Conservative Party lost the 1945 election. For six years he was to serve as the Leader of the Opposition. During these years Churchill continued to influence world affairs; in 1946 he gave his Iron Curtain speech which spoke of the expansionist policies of the USSR and the creation of the Eastern Bloc; Churchill also argued strongly for British independence from the European Coal and Steel Community (which he saw as a Franco-German project as Britain still had an empire). In the General Election of 1951 Labour was defeated and Churchill became Prime Minister for a second time. Churchill continued to lead Britain but was to suffer increasingly from health problems. Aware that he was slowing down both physically and mentally he resigned from the Cabinet in 1955. However he continued to sit as an MP for Woodford until he retired from politics in 1964. Churchill died on 24 January 1965 and was granted the honour of a state funeral. He was buried in his family plot in St Martin's Church, Bladon near to where he was born at Blenheim Palace.
Document 7: Descendants of Winston Churchill: Sir Winston Churchill, son of Lord Randolph Churchill and grandson of John Spencer-Churchill, 7th Duke of Marlborough, was Prime Minister of the United Kingdom between 26 October 1951 – 6 April 1955 and 10 May 1940 – 26 July 1945. In 1908, Churchill married Clementine Hozier, the daughter of Sir Henry and Lady Blanche Hozier. By Clementine, Churchill had five children and ten grandchildren, a number of whom are well known in their own right.
Document 8: Pamela Harriman: Pamela Beryl Harriman ("née" Digby; 20 March 1920 – 5 February 1997), also known as Pamela Churchill Harriman, was an English-born American socialite who was married and linked to important and powerful men. In later life, she became a political activist for the Democratic Party and a diplomat. She was married three times, her first husband being Randolph Churchill, the son of prime minister Winston Churchill. Her only child, Winston Churchill, was named after his famous grandfather.
Document 9: Elspeth Campbell: Elspeth Mary Campbell, Baroness Campbell of Pittenweem (born January 1940) is the wife of the former Liberal Democrat leader Sir Menzies Campbell.
Document 10: Mary Curzon, Baroness Curzon of Kedleston: Mary Victoria Curzon, Baroness Curzon of Kedleston, CI (27 May 187018 July 1906) was a British peeress of American background who was Vicereine of India, as the wife of Lord Curzon of Kedleston, Viceroy of India. As Vicereine of India, she held the highest official title in history of any American woman up to her time.
Document 11: Winston Churchill (1940–2010): Winston Spencer-Churchill (10 October 1940 – 2 March 2010), generally known as Winston Churchill, was a British Conservative Party politician and a grandson of former Prime Minister Sir Winston Churchill. During the period of his prominence as a public figure, he was normally referred to as Winston Churchill, MP, in order to distinguish him from his grandfather. His father Randolph Churchill was also an MP.
Document 12: Emma Soames: Emma Soames (born 9 September 1949) is a British editor. She is the granddaughter of Winston Churchill via her mother Mary, Baroness Soames, and the one-time girlfriend of Martin Amis.
Document 13: Churchill Archives Centre: The Churchill Archives Centre (CAC) is one of the largest repositories in the United Kingdom for the preservation and study of modern personal papers. It is best known for housing the papers of Sir Winston Churchill, the private papers of Baroness Thatcher, and a wide range of political, diplomatic, military and scientific collections, including such well-known modern personalities as: Ernest Bevin, Enoch Powell, Lord Kinnock, Sir John Colville, Lord Hankey, Admiral Lord Fisher, Field Marshal Lord Slim, Sir John Cockcroft, Sir James Chadwick, Professor Lise Meitner, Dr Rosalind Franklin and Sir Frank Whittle.
Document 14: Clarissa Eden: Anne Clarissa Eden, Dowager Countess of Avon ("née" Spencer-Churchill; born 28 June 1920) is the widow of Anthony Eden, 1st Earl of Avon (1897–1977), who was British Prime Minister from 1955 to 1957. She married Eden in 1952, becoming Lady Eden in 1954 when he was made a Knight of the Garter, and then becoming Countess of Avon in 1961 on her husband's elevation to the peerage. She is also the niece of the prime minister Winston Churchill. Her memoir, sub-titled "From Churchill to Eden", was published in 2007 under the name of Clarissa Eden.
Document 15: Clementine Churchill: Clementine Ogilvy Spencer-Churchill, Baroness Spencer-Churchill, ("née" Hozier; 1 April 1885 – 12 December 1977) was the wife of Sir Winston Churchill and a life peer in her own right.
ground_truth: 1 April 1885