Picture posting is enabled for all :)
It's not Blossom End Rot.As the name of the disease implies, symptoms appear only at the blossom end of the fruit.http://vegetablemdonline.ppath.cornell.edu/factsheets/Tomato_BlossRt.htm
So it needs a drink of milk ;D
I hate being technical cos i am not bright enough.I think that means irregular watering......and what causes Blossom End Rot
Maybe Davyw1 can give us some more info on Blackheart Disease in tomatoes, so if we get it we can treat it.
Davy - I haven't had BER for many years here, which I put down to how I water my plants. Now if I ever did get it I would first check the pH of my soil, aiming for 6.5, then I would dose the effected plants with Calcium Nitrate (soluble) in a watering can. The dose can be found online easily enough.
and how on earth could anyone treat Blackheart if you don't know its there till you cut a tomato open, just like BER you wont get it on all the crop.