Potato blight has been rife over the last couple of years because of the poor growing conditions that have been prevalent. Keeping Potatoes well earthed up round the stem can help but keep an eye open for the first tell-tale signs which are brown or black spots at the tips and margins of leaves.
The patches may enlarge and the leaves start to curl and wither with brown patches appearing on the stems. Spread can be rapid throughout the aerial parts of the plant before spreading to the tubers which can then be invaded by secondary infections causing them to rot and give off a foul smell!
All may not be lost if you act as soon as you spot the first signs of the disease. By cutting off all the stems above ground level you may well halt the spread of infection before it reaches the tubers. Make sure the tops are removed from the area and destroyed before lifting the tubers.
It's a good idea to give your Maincrop Potatoes a feed as well. A major cause of poor crops with potatoes is poor nutrition. They are a very greedy plant and a boost now will pay a dividend in tubers. A feed balanced as for tomatoes is ideal.