Actually, the story is not as simple as it may seem, but this is the way it was presented in the Daily Mail.
As often happens in the wild, young cheetahs (or other young predators) have to learn how to catch and how to kill. In many cases, this goes very fast (think about the birds learning to fly when they first try). But cheetahs are known for spending some time at it. Mothers may catch a prey and teach young ones how to kill. Things may take time and the animals seem to be playing with the prey.
The Daily Mail just forgot to provide the real end of the story: The baby impala did not leave the premises alive. It may happen sometimes, not often, but here it was finally killed and eaten.
The photos were shot by Christine and Michel Denis-Huot, clearly some of the very best wildlife photographers in France (Christine is also commonly leading some photo safaris in Africa, you may find information on their web site).
Note: Impalas are really the most common food for cheetahs, probably because of their size (and large numbers in many parts of East and South of Africa).