  We study equilibration and ordering in the classical dipolar kagome Ising
antiferromagnet, which we show behaves as a disorder-free fragile spin glass.
By identifying an appropriate order parameter, we demonstrate a transition to
the ordered state proposed by Chioar et al. [Phys. Rev. B 93, 214410 (2016)]
with a 12-site unit cell that breaks time-reversal and sublattice symmetries,
and further provide evidence that the nature of the transition is first order.
Upon approaching the transition, the spin dynamics slow dramatically. The
system readily falls out of equilibrium, overshooting the transition and
entering a supercooled liquid regime. Using extensive Monte Carlo simulations,
we show that the system exhibits super-Arrhenius behaviour above the ordering
transition. The relaxation time diverges according to a Vogel-Fulcher form at a
finite `glass transition' temperature in the supercooled regime. Such
behaviour, characteristic of fragile glasses, is particularly remarkable as the
model is free of quenched disorder, does not straightforwardly conform to the
avoided criticality paradigm, and is simple and eminently realisable in
engineered nanomagnetic arrays.
