In recent years there has been an explosion in both the amount of next-generation sequencing performed on cancers and in the number of computational methods used to analyse the generated data. Focusing on cancer evolution and heterogeneity, I describe the findings of my research through both large-scale projects such as the International Cancer Genome Consortium and smaller-scale studies of individual tumour types, including prostate, oesophageal, colorectal, breast and haematological cancers. These findings cover a range of topics, including: progression from benign neoplasms to cancer; mechanisms of metastatic spread; changes in mutational processes during cancer progression; variable subclonal response to treatment; the importance of the order of acquisition of driver mutations.