Rotting Aubergine Help Please

Hi,
My Italian neighbour at the plot has been growing Aubergines for years without too much problem. This year he has found them growing perfectly but rotting. Breaking it in half  long ways I would say it is rotting from the outside in. Anyone have any idea what would be causing this? The rot is covering a large area probably about half of the whole fruit. He has never experienced anything like this before so any suggetions would be apprecited. Thanks x

Aubergines can suffer from blossom end rot. Maybe it's that.

I'm not too sure it is blossom end rot. They are rotting on one side lengthways. Am I right thinking the blossom end rot would start on the inside and then rot from the bottom like a tomato?
I don't think he would have ever let them dry out, he is there every single day without fail, unless it is raining hard.
The seed being diseased is an interesting one because he was given the plants this year by somebody who has a plot in another district so he can ask how his are.
Thanks for your input

Googled - thanks, it looks like you were right!