We present the first measurement of an atomic radiative lifetime in Fr. We use a time-correlated single photon counting technique with a cold sample of 210Fr atoms in a magneto-optic trap. The results are a precision experimental test of the atomic many-body perturbation theory applied to the heaviest alkali. The lifetime for the 7p P3y2 level of 21.02s16d ns gives a value for the reduced trans...