Definitely caper berries. Have always been a staple “pickle” in Spanish markets and stores, they are becoming easier and easier to find in London lately.
Great for me as I love them and they are low in carbs.

Here’s a photo from when I last went caper bud picking to preserve my own (used to be quite tricky getting the small capers in salt in my part of Spain, the default there is in vinegar). Ants love them as buds so you have to hang them to dry out, they don’t taste sweet to me but since younger caper buds have 5 times as much carbs as the more mature caper berries the ants must be able to discern the sugar.



So, first you get caper buds, then comes the flower, and I’ve circled the part that grows from the pollinated flower and becomes a caper berry: