  We prove an effective version of a theorem of Dufresnoy: For any set of 2n+1
hyperplanes in general position in n-dimensional complex projective space, we
find an explicit constant K such that for every holomorphic map f from the unit
disc to the complement of these hyperplanes, the derivative of f at the origin
measured with respect to the Fubuni-Study metric is bouned above by K. This
result gives an explicit lower bound on the Royden function, i.e., the ratio of
the Kobayashi metric on the hyperplane complement to the Fubini-Study metric.
Our estimate is based on the potential-theoretic method of Eremenko and Sodin.
