I'm not convinced it's a foxglove/digitalis, even a mutant one.
None of the "mutant foxgloves" pics that we can see on the web show this kind of flowering, the "mutant" flower is always at the top of the stem, the rest of the flowers are normal.
Could you give us more details about that plant. Is it the only one of its kind in your friend's garden? Do any other "normal" foxgloves grow near it (in the garden or in the neighbourhood)? Please take and post photos showing the whole plant in its environment, the basal leaves, close-ups of the stem, the flower-buds, etc. And take the pics with some object nearby to give us an idea of the scale (ideally a measuring tape).
In the meantime maybe some knowledgeable member of this forum (there are many) will identify this curious plant.
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