  We present a detailed modelling study of CD-30$^{\circ}$11223 (CD-30), a hot
subdwarf (sdB)-white dwarf (WD) binary identified as a double detonation
supernova progenitor, using the open-source stellar evolution software MESA. We
focus on implementing binary evolution models carefully tuned to match the
observed characteristics of the system including $\log g$ and $T_{\rm eff}$.
For the first time, we account for the structure of the hydrogen envelope
throughout the modelling, and find that the inclusion of element diffusion is
important for matching the observed radius and temperature. We investigate the
two sdB mass solutions (0.47 and 0.54 $M_{\odot}$) previously proposed for this
system, strongly favouring the 0.47 $M_{\odot}$ solution. The WD cooling age is
compared against the sdB age using our models, which suggest an sdB likely
older than the WD, contrary to the standard assumption for compact sdB-WD
binaries. Subsequently, we propose a possible alternate formation channel for
CD-30. We also perform binary evolution modelling of the system to study
various aspects such as mass transfer, orbital period evolution and luminosity
evolution. Our models confirm CD-30 as a double detonation supernova
progenitor, expected to explode $\approx55$ Myr from now. The WD accretes a
$\approx0.17$ $M_{\odot}$ thick helium shell that causes a detonation, leaving
a 0.30 $M_{\odot}$ sdB ejected at $\approx$750 km/s. The final 15 Myr of the
system are characterised by helium accretion which dominates the system
luminosity, possibly resembling an AM CVn-type system.
