Not a NATO summit, Baxter, but a G7 summit (summit of the seven countries representing the biggest Western economies), on 7-8 May 1977.
Here is another picture of this summit:
And as a non-jewel side note, a funny picture of Canadian Prime Minister Pierre Elliott Trudeau, taken a few minutes before or after the picture above, spinning an unexpected pirouette in Buckingham Palace's Blue Drawing Room:
According to the website linked below (on which I found the picture), the flamboyant and anti-conformistic Trudeau wanted to protest symbolically againt the Palace's protocol, which separated, among the summit's leaders, between the heads of State and the heads of Government: http://iconicphotos.wordpress.com/2009/06/19/trudeaus-pirouette/
--Previous Message-- : Many thanks Baxter. I appreciate the : information. : Beth : : --Previous Message-- : : That photograph is from the Prince of : Wales's Investiture; the date is incorrect : on Getty's site. : : The brooch as shown below was also worn to : the Buckingham Palace dinner held for NATO : leaders in May 1977. : : : : : :