In contrast with most previous studies of activism, we report that the fund executes shareholder activism predominantly through private interventions that would be unobservable in studies purely relying on public information. The fund substantially outperforms benchmarks and we estimate that abnormal returns are largely associated with engagements rather than stock picking. We categorize the engagements and measure their impact on the returns of target companies and the fund. We find that Hermes frequently seeks and achieves significant changes in the company's strategy including refocusing on the core business and returning cash to shareholders, and changes in the executive management including the replacement of the CEO or chairman.