The authors acknowledge the support of the MLDRIN delegates in the preparation of this paper. Jessica Weir has a research agreement with MLDRIN, and has been attending MLDRIN meetings since mid 2003. Steven Ross is the MLDRIN co-ordinator. The authors thank Frances Morphy and Benjamin Smith for organising the workshop which has lead to the creation of this paper. The authors take full responsibility for the content of this paper, including any errors or omissions.