Deformed plums

Yes yes very funny but this is not a joke!!

Quite a few plums on my tree have become a strange shape, a bit gnarly and deformed.

Any idea why?

 

Two reasons for plums going odd shaped. One is insect damage, so look for a tiny puncture wound. There should be a tiny plum stone inside the plum.
If there is no stone in the fruit and they look a bit like bananas then it could(very doubtfully though) be Pocket plum which is a fungal infection. This is not that common in Britain and only then in wet seasons (HAH!) There would be no plum stone in this case.
Either way the treatment is the same, remove and destroy the deformed fruit to prevent further attacks next year.