The article seeks to establish the signiﬁcance of intercepted Greek diplomatic messages as both historical source and catalyst in Britain's Near Eastern policy in the crucial years of 1920–2. Speciﬁcally, the intercepts reveal how members of the British government, foremost among them the prime minister, covertly supported Greek expansion in Asia Minor even after declaring neutrality in the conﬂict. Such evidence conﬁrms rumours that were dismissed as fallacious by those implicated and by their defenders in later historiography. Aside from their value as historical sources, the intercepts had an immediate and significant impact which has also been neglected. Intelligence regarding a distant conﬂict became central to a war at the heart of Westminster and helped mobilize a cross-party, transnational coalition against Lloyd George's foreign policy in the region. Although Lloyd George's opponents, incited by intelligence revelations, eventually succeeded in transforming British policy, this reverse did little to reduce the scale of the resultant catastrophe.