"down to"?

[Joel S. Berson]

 From a BBC story on the discovery of "The Discovery", pornographic
poems inserted into an edition of "The Works of the Earls of
Rochester and Roscommon":

"The success of two best-selling volumes of poetry published in the
18th Century was down to pornographic poems hidden in the book, an
academic has suggested."
http://www.bbc.co.uk/news/entertainment-arts-12365355

Is "down to" a Britishism?  I see it at down, adv., 28.a. "to be down
to: to be attributable to", from 1955.

Joel

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