If you planted your tomatos on the same ground as last year there's an excellent chance of the blight recurring. It is, after all, a fungus. If you didn't do a good job of cleaning up the residue of last years crop it's almost certain the fungus will attach again. One variety of fungus, Alternaria solani also attacks potatoes.
Be sure to move the tomato plantings next year. You can also treat the soil with a product called, here in the U.S., Dormant Oil... it's a smelly sulfur based product one mixes with water and spray on the garden soil at the very first signs of spring warm up. It works very well and is eco-friendly... just don't get any on your shoes and try to come in the house!
Best of luck!
(By the way, as an after thought, be sure to treat your tomatos at least once a week during this apparent attack being sure to spray the undersides of the leaves since the fungus works its way up theplant from the bottom... We've had the best results from a fungicide formulated using chlorothalonil... here a brand name is Bravo...)