The defeat of the UK government’s parliamentary motion on support in principle for military action against the Syrian regime means that Britain will play no part in any direct attack on Syria. What then are its options for resolving the Syrian conflict, protecting civilians and punishing those responsible for war crimes there? This article assesses what the UK can do in terms of pushing for a negotiated peace settlement and to hold accountable those responsible for using chemical weapons and any other war crimes committed during this century’s worst humanitarian crisis.