One-neutron knockout reactions have been performed on a beam of radioactive 53 Co in a high-spin isomeric state. The analysis is shown to yield highly-selective population of high-spin states in an exotic nucleus with a significant cross section, and hence represents a technique that is applicable to the planned new generation of fragmentation-based radioactive beam facilities. Additionally, the relative cross sections among the excited states can be predicted to a high level of accuracy when reliable shell-model input is available. The work has resulted in a new level scheme, up to the 11 + band-termination state, of the proton-rich nucleus 52 Co (Z = 27, N = 25). This has in turn enabled a study of mirror energy differences in the A = 52 odd-odd mirror nuclei, interpreted in terms of isospin-non-conserving (INC) forces in nuclei. The analysis demonstrates the importance of using a full set of J-dependent INC terms to explain the experimental observations.Isospin symmetry arises from the near identical nature of the strong nuclear interaction regardless of which nucleons are involved (e.g. [1]). Under this assumption, and in the absence of electromagnetic effects, the proton and neutron can be considered as two states of the same particle, the nucleon. Heisenberg [2] assigned an isospin quantum number, t = 1 2 for a nucleon, with projection t z = − 1 2 (+ 1 2 ) for the proton(neutron), respectively. For nuclei, therefore, we expect to find isobaric analogue states (IAS), of a given isospin T , in a set of nuclei with T z (= (N − Z)/2) = −T → +T which. In the absence of isospin-breaking terms (such as the electromagnetic interaction), these IAS would be identical and degenerate. In reality, any isospin-breaking interactions will lift this degeneracy, and hence the differences in behaviour between IAS yields direct information on these interactions. Given that the Coulomb interaction is well understood, this has the potential to shed light on how isospin-breaking effects of nuclear origin manifest in nuclei, which is the long-term goal of this study. Mirror energy differences (MED), defined as M ED α = E * α,T,Tz=−1 − E * α,T,Tz=+1 , where α denotes a state label and E * is excitation energy), can yield important information on two-body interactions of the form V pp − V nn that must be used in conjunction with the Coulomb interaction to provide a good theoretical description -see for example [3][4][5][6][7]. These studies have raised fundamental questions about the influence of isovector interactions in nuclear structure. In this Letter, we present a new high-spin study of the odd-odd nucleus 52 Co (Z = 27), the proton-rich member of the T = 1 mirror pair 52 Co/ 52 Mn, using a novel technique to access high-spin states in this exotic system.