  Several sources of repeating coherent bursts of radio emission with periods
of many minutes have now been reported in the literature. These ``ultra-long
period'' (ULP) sources have no clear multi-wavelength counterparts and
challenge canonical pulsar emission models, leading to debate regarding their
nature. In this work we report the discovery of a bright, highly-polarised
burst of radio emission at low Galactic latitude as part of a wide-field survey
for transient and variable radio sources. ASKAP\,J175534.9$-$252749.1 does not
appear to repeat, with only a single intense two-minute $\sim 200$\,mJy burst
detected from 60~hours of observations. The burst morphology and polarisation
properties are comparable to those of classical pulsars but the duration is
more than one hundred times longer, analogous to ULPs. No comparable bursts are
detected in the rest of our widefield survey to date. Combined with the
existing ULP population, this suggests that these sources have a strong
Galactic latitude dependence and hints at an unexplored population of transient
and variable radio sources in the thin disk of the Milky Way. The resemblance
of this burst with both ULPs and pulsars calls for a unified coherent emission
model for objects with spin periods from milliseconds to tens of minutes.
However, whether or not these are all neutron stars or have the same underlying
power source remains open for debate.
