We discuss the phase diagram and phase transitions in U (1)×Z2 three-band superconductors with broken time reversal symmetry. We find that beyond mean field approximation and for sufficiently strong frustration of interband interactions there appears an unusual metallic state precursory to a superconducting phase transition. In that state, the system is not superconducting. Nonetheless, it features a spontaneously broken Z2 time reversal symmetry. By contrast, for weak frustration of interband coupling the energy of a domain wall between different Z2 states is low and thus fluctuations restore broken time reversal symmetry in the superconducting state at low temperatures.In recent years, the discovery of superconductors such as the Iron Pnictides 1 , has generated much interest for multiband superconducting systems. From a theoretical viewpoint, one of the main reasons for the strong interest is that in contrast to previously known two-band materials, iron-based superconductors may exhibit dramatically different physics due to the possibility of frustrated inter-band Josephson couplings originating with more than two bands crossing the Fermi-surface 2-5 . In two-band superconductors the Josephson coupling locks the phase differences between the bands to 0 or π. By contrast, if one has three bands and the frustration of interband coupling is sufficiently strong, the ground state interband phase difference can be different from 0 or π. This leads to a superconducting state which breaks time reversal symmetry (BTRS) 2,3 . From a symmetry viewpoint such a ground state breaks U(1) × Z 2 4 . Recently, such a scenario has received solid theoretical support 5 in connection with hole-doped Ba 1 − x K x Fe 2 As 2 . The possibility of this new physics arising also in other classes of materials is currently under investigation 6 . For other scenarios of time reversal symmetry breakdown in ironbased superconductors discussed in the literature, see 7,8 .Three band superconductors with frustrated interband Josephson couplings feature several properties that are radically different from their two-band counterparts. These include (I) the appearance of a massless so-called Leggett mode at the Z 2 phase transition 9 ; (II) the existence of new mixed phase-density collective modes in the state with broken time-reversal symmetry (BTRS) 4,5,10 in contrast to the "phase-only" Leggett collective mode in two-band materials 11 ; and (III) the existence of (meta-)stable excitations characterized by CP 2 topological invariants 12,13 . So far the phase diagram of frustrated three-band superconductors has been investigated only at the meanfield level 3,5 . However, the iron-based materials feature relatively high T c , as well as being far from the type-I regime. Hence, one may expect fluctuations to be of importance.In this paper, we study the phase diagram of a threeband superconductor in two spatial dimensions in the London limit, beyond mean-field approximation. The results should apply to relatively thin films of ironbased superconducto...