Heatwaves are predicted to increase in frequency and intensity as a result of climate change. The health impacts of these events can be significant, particularly for vulnerable populations when mortality can occur. England experienced a prolonged heatwave in summer 2013. Daily age-group and region-specific all-cause excess mortality during summer 2013 and previous heatwave periods back to 2003 was determined using the same linear regression model and heatwave definition to estimate impact and place observations from 2013 in context. Predicted excess mortality due to heat during this period was also independently estimated. Despite a sustained heatwave in England in 2013, the impact on mortality was considerably less than expected; a small cumulative excess of 195 deaths (95% confidence interval -87 to 477) in 65+ year olds and 106 deaths (95% CI -22 to 234) in <65 year olds was seen, nearly a fifth of excess deaths predicted based on observed temperatures. This impact was also less than seen in 2006 (2323 deaths) and 2003 (2234 deaths), despite a similarly prolonged period of high temperatures. The reasons for this are unclear and further work needs to be done to understand this and further clarify the predicted impact of increases in temperature.