Great Britain's most poisonous mushroom (5,3)

I believe the answer is:

death cap

(Other definitions for death cap that I've seen before include "Killer naturally" , "Poisonous woodland fungus" , "Poisonous fungus -- date chap (anag)" , "Highly poisonous toadstool" , "Poisoner" .)

I've seen this clue in The Times.

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