Question: Casualty had to be rescheduled on March 30, 2002, due to the death of which wife of King George VI?

Context articles: 2002 King George VI and Queen Elizabeth Stakes
George VI Sound
Jamaica 1956-58 £1 chocolate and violet
Silviniaco Conti
Stayers Chase Triple Crown
King George VI Coronation Medal
Casualty (series 16)
George VI and Queen Elizabeth Memorial
Kauto Star Novices' Chase
Queen Elizabeth The Queen Mother

The 2002 King George VI and Queen Elizabeth Stakes was a horse race held at Ascot Racecourse on Saturday 27 July 2002.
 It was the 52nd King George VI and Queen Elizabeth Stakes.
George VI Sound or Canal Jorge VI or Canal Presidente Sarmiento or Canal Seaver or King George VI Sound or King George the Sixth Sound is a major bay/fault depression, 300 miles (483 km) long in the shape of the letter J, which skirts the east and south shores of Alexander Island, separating it from Palmer Land, in the southern portion of the Antarctic Peninsula and the English Coast.
 Various lakes are adjacent to the sound, these lakes receive large amounts of ice flowing from George VI Ice Shelf into the mouth of these lakes.
 Some of these include Hodgson Lake, Moutonnee Lake and Ablation Lake.
 Several glaciers also flow eastward into the sound from the east interior of Alexander Island, the vast majority of these glaciers are situated south of Planet Heights, where all of these glaciers are named after moons, satellites and planets of the solar system in association with nearby Planet Heights which was named by the United Kingdom Antarctic Place-Names Committee (UK-APC) in 1977.
The Jamaica 1956 £1 chocolate and violet was a planned, but unissued, Jamaican postage stamp.
 The stamp's design was identical to the King George VI stamp, issued in 1949, which depicted a scene of workers rolling cigars by hand, but with the vignette image of King George VI replaced with that of Queen Elizabeth II.
 Although the stamp was abandoned after printing and not issued, there are seven copies in existence.
 It was replaced by a £1 stamp depicting Jamaica's coat of arms.
Silviniaco Conti (foaled 14 April 2006) is a French-bred, British-trained Selle Francais racehorse who competed in National Hunt races.
 After winning several important races over hurdles he emerged as a leading long-distance steeplechaser in 2012.
 After winning both his races in his native country, the horse won his first three races in England, culminating with a success in the two and a half mile Ascot Hurdle.
 After running poorly over shorter distances he was ruled out of a bid for the Champion Hurdle and was switched to steeplechasing.
 In his first season as a chaser he won the Mildmay Novices' Chase and finished second in a strong renewal of the Feltham Chase.
 In the 2012/2013 season he won the Charlie Hall Chase, Betfair Chase and Denman Chase and in the following season he was rated the best jumper in Britain and Ireland after wins in the King George VI Chase and Betfred Bowl.
 In the 2014/2015 season he recorded repeat victories in the Betfair Chase, King George VI Chase and Betfred Bowl but failed when favourite for the Cheltenham Gold Cup.
 In the following season he was beaten in his first three races but returned to form in February to win the Grade One Ascot Chase by 20 lengths.
The Stayers Chase Triple Crown was an Betfair initiative started in 2005 called 'Betfair Million' to award £1 million prize for any horse who wins in the same season the Betfair Chase at Haydock in November, the King George VI Chase at Kempton on Boxing Day and the Cheltenham Gold Cup at the Cheltenham Festival.
 In the following season it suffered a couple alterations which included the Lexus Chase as an alternative for the King George VI Chase or winning the Grand National whilst being placed in top two at any race at the Cheltenham Festival.
The King George VI Coronation Medal was a commemorative medal, instituted to celebrate the coronation of King George VI and Queen Elizabeth.
The sixteenth series of the British medical drama television series "Casualty" commenced airing in the United Kingdom on BBC One on 15 September 2001 and finished on 29 June 2002.
 It saw another increase, this time to 40 episodes.
 On 30 March 2002, Episode 350 had to be shown on BBC Two, due to some schedule changes on BBC One, the Queen Mother had died that day.
The George VI and Queen Elizabeth Memorial, situated between The Mall and Carlton Gardens in central London, is a memorial to King George VI and his consort, Queen Elizabeth The Queen Mother.
 Completed in its present form in 2009, the memorial incorporates an earlier, Grade II-listed statue of George VI by William McMillan, unveiled by his daughter Queen Elizabeth II in 1955.
 The reconfigured memorial, which includes a statue of the Queen Mother by Philip Jackson, relief sculpture by Paul Day and an architectural setting by Donald Buttress and Donald Insall, was unveiled by Elizabeth II in 2009.
The Kauto Star Novices' Chase is a Grade 1 National Hunt chase in Great Britain which is open to horses aged four years or older.
 It is run at Kempton Park over a distance of about 3 miles (4,828 metres), and during its running there are eighteen fences to be jumped.
 The race is for novice chasers, and it is scheduled to take place each year during the King George VI Chase meeting on Boxing Day.
 The race was originally known as the Feltham Novices' Chase.
 The 2012 running additionally carried the name of Kauto Star (a winner of the King George VI Chase on five occasions) pending a permanent change of name.
 The permanent name change was confirmed by the BHA in July 2013.
Elizabeth Angela Marguerite Bowes-Lyon (4 August 1900 – 30 March 2002) was the wife of King George VI and the mother of Queen Elizabeth II and Princess Margaret, Countess of Snowdon.
 She was Queen of the United Kingdom and the Dominions from her husband's accession in 1936 until his death in 1952, after which she was known as Queen Elizabeth The Queen Mother, to avoid confusion with her daughter.
 She was the last Empress of India.