I just got back from my mother's and noticed this spot on one of my tomato plants. I had these last year, and had retrospectively diagnosed them a the beginning of the blight. But I don't know for sure. I have some blight resistant varieties, but this is on Gardener's Delight plant. Looking back through this thread topic, I noticed the posts on the 23rd June last year.
Not sure I could stand an other repeat of last year's heartache.