  We consider the H to gamma gamma decay process and the gluon fusion
production of a light Higgs, and provide a general framework for testing models
of new physics beyond the Standard Model. We apply our parametrisation to
typical models extending the Standard Model in 4 and 5 dimensions, and show how
the parametrisation can be used to discriminate between different scenarios of
new physics at the Large Hadron Collider and at future Linear Colliders.
