  We consider partial supersymmetry breaking in ${\cal N}=2$ supergravity
coupled to a single vector and a single hypermultiplet. This breaking pattern
is in principle possible if the quaternion-K\"ahler space of the hypermultiplet
admits (at least) one pair of commuting isometries. For this class of
manifolds, explicit metrics exist and we analyse a generic electro-magnetic
(dyonic) gauging of the isometries. An example of partial breaking in Minkowski
spacetime has been found long ago by Ferrara, Girardello and Porrati, using the
gauging of two translation isometries on $SO(4,1)/SO(4)$. We demonstrate that
no other example of partial breaking of ${\cal N}=2$ supergravity in Minkowski
spacetime exists. We also examine partial-breaking vacua in anti-de Sitter
spacetime that are much less constrained and exist generically even for
electric gaugings. On $SO(4,1)/SO(4)$, we construct the partially-broken
solution and its global limit which is the Antoniadis-Partouche-Taylor model.
