We have learnt that Queen Victoria inherited it from Queen Adelaide in 1837, when it passed to her along with the other jewels that were associated with the Crown.
We have also been informed owning to the QD that Queen Mary in 1911 removed three stones from Queen Adelaide's Collet necklace, which were used to lengthen 'The Coronation Necklace'.
In 1911, a collection of 154 loose diamond collets were held in store at Garrard, marked ‘C’ for Crown (From the QD, Twinings and Menkes).
Consequently, we can suppose that these were the diamonds remaining from ‘Queen Adelaide’s Collet Necklace’
In 1950, King George VI commissioned Garrard to use 115 of these loose stones to create the festoon necklace.
He gave this necklace to Queen Elizabeth II whilst she was still Princess Elizabeth.
We also know that Queen Elizabeth wore ont least once this necklace.
Apparently, the necklace weights at the origin 170 carats.
Roberts described this necklace as being “composed of 83 brilliants in cut-down collets, the three largest cushion-shaped, set as three graduated chains suspended from triangular clasps at either side, pavé-set with a further 22 stones, and joined by a single back-chain with clasp”.
In 1953 this necklace was later shortened by 10 stone, so that it now consists of 105 stones in total.
In conclusion, the festoon necklace must be made from Queen Adelaide's necklace