  Higher Education Institutions in the UK and elsewhere are under increasing
pressure to measure the impact of their research, which can include how the
research has increased scientific engagement amongst the general public. For
various reasons, the need for evidence can arise months, or even years, after a
particular research discovery has been made. Furthermore, the right kind of
evidence is needed to indicate genuine behavioural change amongst a given
target audience, which can be difficult to obtain after time has passed. In
this article, we present a number of strategies for retrospective evidencing of
research engagement, and illustrate their use on example discoveries from up to
five years ago.
