  The Direct Collapse Black Hole (DCBH) scenario provides a solution for
forming the massive black holes powering bright quasars observed in the early
Universe. A prerequisite for forming a DCBH is that the formation of (much less
massive) Population III stars be avoided - this can be achieved by destroying
H$_2$ via Lyman-Werner (LW) radiation (E$_{\rm{LW}}$ = 12.6 eV). We find that
two conditions must be met in the proto-galaxy that will host the DCBH. First,
prior star formation must be delayed; this can be achieved with a background LW
flux of J$_{\rm BG} \gtrsim 100\ J_{21}$. Second, an intense burst of LW
radiation from a neighbouring star-bursting proto-galaxy is required, just
before the gas cloud undergoes gravitational collapse, to finally suppress star
formation completely. We show here for the first time using high-resolution
hydrodynamical simulations, including full radiative transfer, that this
low-level background, combined with tight synchronisation and irradiation of a
secondary proto-galaxy by a primary proto-galaxy, inevitably moves the
secondary proto-galaxy onto the isothermal atomic cooling track, without the
deleterious effects of either photo-evaporating the gas or polluting it by
heavy elements. These, atomically cooled, massive proto-galaxies are expected
to ultimately form a DCBH of mass $10^4 - 10^5 M_{\odot}$.
