Some years ago, a book was published in Moscow (Олег Шишкин, Убить Распутина, М., 2000), the author of which, Oleg Shishkin states that Samuel Hoare, in 1916 a liason officer in Moscow, was among the murderers of Rasputin and in fact lead the assasination, the other participants being inexpert in the art of killing. Part of the evidence is the fact that Nicolas II himself considered Hoare guilty of the murder, ordering him out of Russia.
It would be interesting to know if something in the sense has transpired in Western sources.
Samuel Hoare, murderer of Rasputin
Re: Samuel Hoare, murderer of Rasputin
Googling Samuel Hoare murder of rasputin turns up numerous hits. Start there.