|Queen Mary and many, many diamond necklaces|
The Coronation Necklace would also fall under this category, with the Lahore pendant removed.
Queen Alexandra's Collet Necklace
|Queen Alexandra wears the necklace on a velvet choker|
The Duchess of Teck's Collet Necklace
|Queen Mary (left), and Queen Elizabeth (right), both wearing the Teck necklace as the longest necklace|
Queen Elizabeth's Coronation Necklace
|Queen Elizabeth (left, with the Coronation Necklace), and the Duchess of Cornwall|
Longer, Graduated Collet Necklace
Smaller Collet Necklace
This list is not complete and the Queen's collection almost certainly includes more examples, but these necklaces are devilishly hard to tell apart when in use. They can also be varied in length, as Queen Mary did. Identifications are always up for debate.
Many thanks to Franck for additional identifications, and also to Baxter.
19 November 2012: Royal Variety Performance (Longer, graduated)
27 July 2012: Opening Ceremony of the London Olympics (Smaller)
2010: State Visit to the UAE and Oman (Longer, graduated)
2010: Visit to Canada (Queen Alexandra's)
2008: State Visit from France (Queen Elizabeth's, on the Duchess of Cornwall)
Photos: Royal Collection/PA/via Getty Images