The first settlers in Tasmania took prime farm land from Aboriginals without a qualm or conscience: they had a piece of paper saying it was their's, completely disregarding the native inheritance of the land from their ancestors for thousands of years. When the Aborigines fought back in the early 19th century it led to bitter battles over decades before the Australian government sent in the army to sort it out once and for all. The Aborigines were banished to the forest and given a piece of paper saying it was theirs. So that's all right then.It was probably the unintended effects of European diseases that caused their decline.
Same thing happened in America, the common cold wiped out most of the Eskimo population.
So not really genocide in the strict sense of the word.
Nothing to do with the British government.