This work is an investigation of how a software architecture can be changed in order to improve the support of the creation of a customised user interface. The parts of Symbian OS that are of interest for the work are described in detail. Then a comparison of the user interfaces of four different mobile devices is made, in order to get a picture of what the interfaces of such devices could look like. Also presented in the work is a modified reference architecture that supports customisation of all the features that have been identified in the comparison. Finally, the authors discuss how well the new architecture supports customisation of the user interface compared to the original Symbian OS architecture.