Although croquet had been played in Victoria (at Kyneton) since at least 1866, the Victorian Croquet Association was not formed until 1914 and affiliated with the (English) Croquet Association in 1917. After this affiliation it acted as the governing body in Australia and was so recognised by the Croquet Association - at this time, and for some time after, Victoria was the strongest croquet state.
Immediate attempts were made to arrange a challenge match between the two countries, but World War 1 intervened and it wasn't until Australia issued a challenge in 1924, which was accepted by the Croquet Association, that a test series was arranged to take place in England in 1925.
Victoria contacted the other states, requesting nominees for the team, which were received from Queensland and New South Wales, although the NSW nominee later withdrew, and the Queensland representative, Mrs H Dinsdale accompanied the team as the Reserve.
In February 1925, Mr MacPherson Robertson's offer of a silver mounted shield for international competition was accepted by the Victorian Croquet Association and was despatched, following the team, which was already in England. That challenge match was won by England. The return challenge, held in Australia in 1927, was won by Australia.
New Zealand joined the competition in 1930, but England did not compete. All competed in 1935, but New Zealand did not compete in England in 1937. Since then, all nations have competed, with the United States of America joining in 1993.
The shield has been contested at, initially, irregular periods from 1925, with the 1925, 1927, 1930, 1935 and 1937 Australian teams consisting solely of Victorians.
There was a 13-year hiatus during and following WW2, between 1937 and 1950.
In 1950, the Australian Croquet Council was formed and became the governing body of Australian croquet for national and international competitions but did not enter a challenge until 1963, when a team was sent to New Zealand.
Great Britain contested the 1974, 1979, 1982, and 1986 events, Great Britain and Ireland the 1990 and 1993 events, reverting to Great Britain for the 1996, 2000, 2003, 2006, and 2010 events, reverting further to England for the 2014 and subsequent events.
New Zealand joined the competition in 1930 and the United States in 1993.
The MacRobertson Shield had been organised and contested by the competitors, but in 2010 came under the aegis of the World Croquet Federation.
More information about Sir Macpherson Robertson can be found on Wikipedia
Previous Winners (details on Wikipedia: https://en.wikipedia.org/wiki/MacRobertson_International_Croquet_Shield)
https://www.croquetrecords.com/records/mac/mac2013.htm