Continue harvesting first and second early potatoes as and when needed, but keep a look out for symptoms of blight. These are black patches appearing on the leaves followed by a white looking powder around the edges which are the spores of the fungus.
Again, don’t despair too much because if spotted quickly enough and action taken, the potatoes underground should be unaffected.
Cut all the foliage off the affected plant and burn it or bag it up to dispose of it. Never put it on a compost pile or leave it lying around as the spores can quickly land on other potato plants. Wait at least 3 weeks before harvesting potatoes from an infected plant to avoid them being infected by the blight spores on top of the soil.