UK law allows for the prosecution of international crimes under a principle known as ‘universal jurisdiction’. Universal jurisdiction allows the courts of any country to hold trials for crimes that ‘shock the conscience’ – including genocide, crimes against humanity, and war crimes – no matter where they occur. But legal constraints, practical challenges, and a lack of political will have meant that only three people have been convicted of such crimes in the UK – ever. This report sets out reforms that would close loopholes and allow for more successful cases to be brought in English courts against suspects of the most serious international crimes.