  The International Linear Collider has a rich physics programme, whatever lies
beyond the standard model. Accurate measurement of the top quark mass is needed
to constrain the model or its extensions. If there is a light Higgs boson the
LHC should see it, but the ILC will pin down its characteristics and test them
against model predictions. If Supersymmetric particles appear the ILC will
measure a complementary set of them to those seen at the LHC, and may allow
extrapolation to the Grand Unified scale. And if a strong electroweak sector is
indicated the ILC will be sensitive to the presence of new structures in
difermion and diboson systems up to higher masses than the direct search range
of the LHC. Beyond the LHC and ILC there could be need for a multi TeV lepton
collider.
