What's wrong with this tomato plant?

[Bledlow]

The plant itself doesn't look too bad, though the stem & branches are very thick, the leaves thick, & the whole thing goes curly at the top, but the tomatoes (of which there are far fewer than on the other plants) are disastrously bad.
Plant


Tomatoes


They're all going like that as they grow. Only one plant affected, luckily: the tomatoes on the others are plentiful & looking perfectly normal.

Is it a disease? A nutrient problem? Something I can do something about? Or should I just give up on this plant & scrap it?

[numbnuts]

  Where did you get the seeds/plants from Chernobyl

[Cudzoziemiec]

I remember my grandfather's tomatoes growing rather like the one on the right - I think it was a viral disease. But none of them were like the one on the right, and it's just a vague memory from many years ago. Not much help, sorry.