  We present results from radio and X-ray observations of the X-ray transient
MAXI J1810-222. The nature of the accretor in this source has not been
identified. In this paper, we show results from a quasi-simultaneous radio and
X-ray monitoring campaign taken with the Australia Telescope Compact Array
(ATCA), the Neil Gehrels Swift observatory X-ray telescope (XRT), and the Swift
Burst Alert Telescope (BAT). We also analyse the X-ray temporal behaviour using
observations from the Neutron star Interior Composition Explorer (NICER).
Results show a seemingly peculiar X-ray spectral evolution of MAXI J1810-222
during this outburst, where the source was initially only detected in the soft
X-ray band for the early part of the outburst. Then, ~200 days after MAXI
J1810-222 was first detected the hard X-ray emission increased and the source
transitioned to a long-lived (~1.5 years) bright, harder X-ray state. After
this hard state, MAXI J1810-222 returned back to a softer state, before fading
and transitioning again to a harder state and then appearing to follow a more
typical outburst decay. From the X-ray spectral and timing properties, and the
source's radio behaviour, we argue that the results from this study are most
consistent with MAXI J1810-222 being a relatively distant ($\gtrsim$6 kpc)
black hole X-ray binary. A sufficiently large distance to source can simply
explain the seemingly odd outburst evolution that was observed, where only the
brightest portion of the outburst was detectable by the all-sky X-ray
telescopes.

High Energy Astrophysical Phenomena