  We report on the near-infrared polarimetric observations of G11.11-0.12
(hereafter G11) obtained with SIRPOL on the 1.4 m IRSF telescope. The starlight
polarisation of the background stars reveals the on-sky component of magnetic
fields in G11, and these are consistent with the field orientation observed
from polarised dust emission at $850\,\mu$m. The magnetic fields in G11 are
perpendicular to the filament, and are independent of the filament's
orientation relative to the Galactic plane. The field strength in the envelope
of G11 is in the range $50-100\,\mu$G, derived from two methods. The analyses
of the magnetic fields and gas velocity dispersion indicate that the envelope
of G11 is supersonic but sub-Alfv{\'e}nic. The critical mass-to-flux ratio in
the envelope of G11 is close to 1 and increases to $\gtrsim 1$ on the spine of
G11. The relative weights on the importance of magnetic fields, turbulence and
gravity indicate that gravity dominates the dynamical state of G11, but with
significant contribution from magnetic fields. The field strength,
$|\mathbf{B}|$, increases slower than the gas density, $n$, from the envelope
to the spine of G11, characterized by $|\mathbf{B}|\propto n^{0.3}$. The
observed strength and orientation of magnetic fields in G11 imply that
supersonic and sub-Alfv{\'e}nic gas flow is channelled by the strong magnetic
fields and is assembled into filaments perpendicular to the magnetic fields.
The formation of low-mass stars is enhanced in the filaments with high column
density, in agreement with the excess of low-mass protostars detected in the
densest regions of G11.
