  Pulsars are highly-magnetised rotating neutron stars and are well-known for
the stability of their signature pulse shapes, allowing high-precision studies
of their rotation. However, during the past 22 years, the radio pulse profile
of the Crab pulsar has shown a steady increase in the separation of the main
pulse and interpulse components at 0.62$^{\rm o}\pm$0.03$^{\rm o}$ per century.
There are also secular changes in the relative strengths of several components
of the profile. The changing component separation indicates that the axis of
the dipolar magnetic field, embedded in the neutron star, is moving towards the
stellar equator. This evolution of the magnetic field could explain why the
pulsar does not spin down as expected from simple braking by a rotating dipolar
magnetic field.
