  Over the past several decades, galaxy formation theory has met with
significant successes. In order to test current theories thoroughly we require
predictions for as yet unprobed regimes. To this end, we describe a new
implementation of the Galform semi-analytic model of galaxy formation. Our
motivation is the success of the model described by Bower et al. in explaining
many aspects of galaxy formation. Despite this success, the Bower et al. model
fails to match some observational constraints and certain aspects of its
physical implementation are not as realistic as we would like. The model
described in this work includes substantially updated physics, taking into
account developments in our understanding over the past decade, and removes
certain limiting assumptions made by this (and most other) semi-analytic
models. This allows it to be exploited reliably in high-redshift and low mass
regimes. Furthermore, we have performed an exhaustive search of model parameter
space to find a particular set of model parameters which produce results in
good agreement with a wide range of observational data (luminosity functions,
galaxy sizes and dynamics, clustering, colours, metal content) over a wide
range of redshifts. This model represents a solid basis on which to perform
calculations of galaxy formation in as yet unprobed regimes.
