  A precision test of lepton flavour universality has been performed by
measuring the ratio RK of kaon leptonic decay rates K+ --> e+nu and K+ -->
mu+nu in a sample of 59813 reconstructed K+ --> e+nu candidates with (8.71 +-
0.24)% background contamination. The result RK = (2.487 +- 0.013) * 10^{-5} is
in agreement with the Standard Model expectation.
