A Singing Christmas Tree, sometimes called a Living Christmas Tree, is an artificial Christmas tree filled with singers used as part of nativity plays. First appearing in 1933 at Belhaven University, they later made their debut indoors at West High School in Denver, Colorado, and then in 1957 in Sacramento, California.
 Constructed of steel, the tree is actually a conical circular sector where between one-third and one-half of an actual Christmas tree is shown.
 Depending upon tree size, they can accompany between 30 and 450 singers.
 These trees can be put up by churches or communities depending upon the location.
 Since then, the singing Christmas tree concept has spread to Canada, the Philippines, South Korea, Switzerland and Sri Lanka.
 The most attended tree takes place in Knoxville, Tennessee, with 60,000 attendees in 2007.
A Christmas tree stand is an object designed to support a cut, natural or an artificial Christmas tree.
 Christmas tree stands appeared as early as 1876 and have had various designs over the years.
 Those stands designed for natural trees have a water-well, which, in many cases may not hold enough water to adequately supply the cut tree.
 Some specialty Christmas tree stands have value on the secondary antiques market.
Christmas tree production occurs worldwide on Christmas tree farms, in artificial tree factories and from native strands of pine and fir trees.
 Christmas trees, pine and fir trees purposely grown for use as a Christmas tree, are grown on plantations in many western nations, including Australia, the United Kingdom and the United States.
 In Australia, the industry is relatively new, and nations such as the United States, Germany and Canada are among world leaders in annual production.
While the first Christmas tree farm may have appeared as early as 1901, Christmas tree production in the United States was largely limited to what could be harvested from natural forests until the 1950s.
 Among the important Christmas tree producing areas in the U.S. are Wisconsin, North Carolina, Pennsylvania and the Pacific Northwest.
 In 2002 Christmas tree production in the United States totaled 20.8 million trees and the U.S. was one of the world's leading producers of natural Christmas trees.
 That same year, Pennsylvania was the top producer in the United States.
The Mount Ingino Christmas Tree is a lighting illumination in the shape of a Christmas tree that is installed annually on the slopes of Mount Ingino (Monte Ingino in Italian) outside the city of Gubbio, in Umbria region in Italy.
 The tree is also called the Gubbio Christmas Tree or "the biggest Christmas tree in the world".
 In 1991 the Guinness Book of Records named it "The World's Largest Christmas Tree".
The Trafalgar Square Christmas tree is a Christmas tree donated to the people of Britain by the city of Oslo, Norway each year since 1947.
 The tree is prominently displayed in Trafalgar Square from the beginning of December until 6 January.
The White House Christmas Tree, also known as the Blue Room Christmas Tree, is the official indoor Christmas tree at the residence of the President of the United States, the White House.
 The first indoor Christmas tree was installed in the White House sometime in the 19th century (there are varying claims as to the exact year) and since 1961 the tree has had a themed motif at the discretion of the First Lady of the United States.
An aluminum Christmas tree is a type of artificial Christmas tree that was popular in the United States from 1958 until about the mid-1960s.
 As its name suggests, the tree is made of aluminum, featuring foil needles and illumination from below via a rotating color wheel.
 The aluminum Christmas tree was used as symbol of the commercialization of Christmas in the highly acclaimed and successful 1965 television special, "A Charlie Brown Christmas", which discredited its suitability as holiday decoration.
 By the mid-2000s aluminum trees found a secondary market online, often selling for high premiums.
 The trees have also appeared in museum collections.
The National Christmas Tree is a large evergreen tree located in the northeast quadrant of The Ellipse near the White House in Washington, D.C. Each year since 1923, the tree has been decorated as a Christmas tree.
 Every early December, the tree is traditionally lit by the President of the United States.
 Every president since Franklin D. Roosevelt has made formal remarks during the tree lighting ceremony.
 Since 1954, the event has marked the start of month-long festivities known as the Pageant of Peace.
 Smaller trees representing the U.S. states, District of Columbia, and the five territories around the National Christmas Tree are referred to as the Pathway to Peace.
Alfhild Hovdan (née Olsen; 13 September 1904 – 20 February 1982) was a Norwegian journalist, and later tourist manager for the city of Oslo for more than forty years.
 She is known for initiating the tradition of the Trafalgar Square Christmas tree, a present from the city of Oslo to the people of London, in recognition of their assistance during World War II.

Question: What year did Alfhild Hovdan initiate the tradition of donating a christmas tree to the people of Britain?
Answer: 1947