Something looking like a pepper grows among chilli plants has seeds that look like chilli seeds but is solidly-fleshed bright red and spherical about the size of a child's marble It has no pungency?
Answered my own question with the help of the local herbarium. It's a Jerusalem cherry and it's poisonous (though clearly not to the birds who keep planting them). Very decorative; I've moved the plants into pots in the front garden where the dog can't chew them. Before I checked on it I was ready to taste the berries of what I now know to be Solanum pseudocapsicum, thinking it would make a good salad garnish, but one of my sons said, it might look like a chilli but it looks poisonous to me. Thanks for that, Mick.