We were able to discover two new kinds of atomic species, one was hydrogen of mass 3, unknown until that time, and the other helium of mass 3, also unknown. … We were able to show that heavy hydrogen nuclei, that is to say the cores of heavy hydrogen atoms, could be made to react with one another to produce a good deal of energy and new kinds of atom. …Of course, we had no idea whatever that this would one day be applied to make hydrogen bombs. Our curiosity was just curiosity about the structure of the nucleus of the atom, and the discovery of these reactions was purely, as the Americans would put it, coincidental.

On his research on atomic nuclei with Ernest Rutherford, p. 24 - Portraits in Science interviews (1994)