  We present new high-resolution and high-sensitivity studies of the jets in
the WAT source 3C 465, using deep transverse-resolved radio observations from
e-MERLIN, and with complementary observations from the VLA. We derive a lower
limit $\beta_{\rm j}$ = ($\nu_{\rm j}$/$c$) $\gtrsim$ 0.5 for the jet speed,
and an upper limit $\theta_{\rm j}$ $\lesssim$ 61$^{\circ}$ for the jet angle
to the line of sight. The jet spectral index ($\alpha$, defined in the sense $S
\propto \nu^{\alpha}$) is fairly constant (<$\alpha_{\rm jet}$> = $-$0.7), and
spectral flattening within 4.4 kpc of the core coincides with bright knots and
is consistent with the site of X-ray particle acceleration at the base of the
radio jet found in previous studies. There is little difference between the
spectra of the two hotspot components, plausibly indicating that electron
populations of the same properties are injected there. The NW and SE plumes are
approximately homologous structures, with variations in mass injection and
propagation in external pressure and density gradients in the two regions
plausibly accounting for the slightly steeper spectrum in the NW plume,
<$\alpha_{\rm NWp}$> = $-$1.43 compared with the SE plume, <$\alpha_{\rm SEp}$>
= $-$1.38. Our synchrotron lifetime model supports plausible reacceleration of
particles within the plume materials. Overall, our results show that the
first-order Fermi process at mildly relativistic and non-relativistic shocks is
the most likely acceleration mechanism at play in 3C 465 and distinguish
differences between the acceleration at $\beta_{\rm j}$ $>$ 0.5 and $\beta_{\rm
j}$ $<$ 0.5. The former case can accelerate electrons to higher Lorentz
factors.
