Sometimes it's difficult to track these things down, considering that the interwebs use the same photos for different stories. Anyway, the second photo with the pink dress is from the Golden Globes:
"Helen Mirren made a striking appearance at the Golden Globes Golden Eve event, showcasing a stunning 241-carat tourmaline necklace designed by Margot McKinney. The necklace, part of McKinney's Bloem Collier collection, featured a centrepiece gem weighing 65.85 carats and was adorned with 27 Australian South Sea baroque pearls, as well as a mix of diamonds and sapphires."
Btw, the pearl earrings Helen wore to the Buckingham Palace event were small and tasteful, appropriate for the occasion.