  Decayless kink oscillations of plasma loops in the solar corona may contain
an answer to the enigmatic problem of solar and stellar coronal heating. The
polarisation of the oscillations gives us a unique information about their
excitation mechanisms and energy supply. However, unambiguous determination of
the polarisation has remained elusive. Here, we show simultaneous detection of
a 4-min decayless kink oscillation from two non-parallel lines-of-sights,
separated by about 104\textdegree, provided by unique combination of the High
Resolution Imager on Solar Orbiter and the Atmospheric Imaging Assembly on
Solar Dynamics Observatory. The observations reveal a horizontal or weakly
oblique linear polarisation of the oscillation. This conclusion is based on the
comparison of observational results with forward modelling of the observational
manifestation of various kinds of polarisation of kink oscillations. The
revealed polarisation favours the sustainability of these oscillations by
quasi-steady flows which may hence supply the energy for coronal heating.
