  We argue that the complex transformation relating the Schwarzschild to the
Taub-NUT metric, introduced by Talbot, is in fact an electric-magnetic duality
transformation. We show that at null infinity, the complex transformation is
equivalent to a complexified BMS supertranslation, which rotates the
supertranslation and the dual (magnetic) supertranslation charges. This can
also be seen from the cubic coupling between the classical source and its
background, which for Taub-NUT is given by a complex phase rotation acting on
gravitational minimal couplings. The same phase rotation generates dyons from
electrons at the level of minimally coupled amplitudes, manifesting the double
copy relation between the two solutions.
