A fascination with chromosomes, especially chromosomal aberrations, li
nked many at the Oak Ridge National Laboratory and the Medical Researc
h Council Radiobiological Research Unit at Harwell, but they disagreed
about the correctness of Revell's exchange hypothesis. This is a pers
onal story of how a critical test of this hypothesis was conceived, wi
th glimpses of life in the two centres. (C) 1994 Wiley-Liss, Inc.