The Chef has ridged up (or earthed up) the first lot of potatoes that he planted in the plot.
potatoes ridged up
These Maris Bard potatoes were planted on 2nd April, 40 days ago. The tops were 9 inches above the surface of the ground. They were planted quite shallow.
It is important to get a good depth of soil over the seed potato, as the root ball will grow around this and push out stolons which form potatoes on the ends. These new potatoes must have a good covering of soil to protect them from daylight. If the new potatoes are exposed to light they go green, which renders them poisonous.