If the impact of positive environmental announcements on corporate valuations is positive markets can provide a vital mechanism through which to address climate change, plastic pollution, and fertiliser runoff. Thus, this thesis looks at this impact of positive environmental actions on large UK corporations 2011-2019, via several event studies. There is also analysis of the likely role of institutional investors, selection bias and new entrants to the FTSE 100. The key finding is that the announcement of new environmental initiatives leads to a positive, statistically significant, and economically material 0.6% abnormal weekly return. Several other types of positive environmental news are found to be undistinguishable from non-events. This provides a more nuanced and asset pricing consistent understanding than much of the existing literature.