Firm-level investment paths are commonly characterised by periods of low or zero investment punctuated by large investment ‘spikes’. We document that such spikes are important for understanding ﬁrm and aggregate level investment in the UK. We show that annual variation in aggregate investment is driven by variation in the number of ﬁrms undertaking investment spikes rather than in the size of spikes or in investment outside of spikes. Our main contribution is to set out and estimate a ﬁrm-level model of the timing of investment spikes that: (i) incorporates measures of macroeconomic conditions and can be used to replicate movements in aggregate investment; (ii) incorporates a role for ﬁrm capital structure, which we demonstrate explains part of ﬁrms’ heterogeneous investment responses to the Great Recession. We ﬁnd an important role for low demand growth in depressing investment in the recession and for ongoing uncertainty in prolonging investment weakness in later years. The minority of ﬁrms that persistently operate with high debt levels were signiﬁcantly less likely to undertake an investment spike after the recession, which is consistent with them having been more exposed to ﬁnancial distress.