  Young massive clusters (YMCs) are compact ($\lesssim$1 pc), high-mass
(>10${}^4$ M${}_{\odot}$) stellar systems of significant scientific interest.
Due to their rarity and rapid formation, we have very few examples of YMC
progenitor gas clouds before star formation has begun. As a result, the initial
conditions required for YMC formation are uncertain. We present high-resolution
(0.13$^{\prime\prime}$, $\sim$1000 au) ALMA observations and Mopra single-dish
data, showing that Galactic Centre dust ridge `Cloud d' (G0.412$+$0.052,
mass$\sim 7.6 \times 10^4$ M$_{\odot}$, radius$\sim 3.2$ pc) has the potential
to become an Arches-like YMC (10$^4$ M$_{\odot}$, r$\sim$1 pc), but is not yet
forming stars. This would mean it is the youngest known pre-star forming
massive cluster and therefore could be an ideal laboratory for studying the
initial conditions of YMC formation. We find 96 sources in the dust continuum,
with masses $\lesssim$3 M$_{\odot}$ and radii of $\sim$10${}^3$ au. The source
masses and separations are more consistent with thermal rather than turbulent
fragmentation. It is not possible to unambiguously determine the dynamical
state of most of the sources, as the uncertainty on virial parameter estimates
is large. We find evidence for large-scale ($\sim$1 pc) converging gas flows,
which could cause the cloud to grow rapidly, gaining 10$^4$ M$_{\odot}$ within
10$^5$ yr. The highest density gas is found at the convergent point of the
large-scale flows. We expect this cloud to form many high-mass stars, but find
no high-mass starless cores. If the sources represent the initial conditions
for star formation, the resulting IMF will be bottom-heavy.
