2011 was the fiftieth anniversary of the negotiation, at the height of the cold war, of the 1961 Vienna Convention on Diplomatic Relations (VCDR). Since then the VCDR has become a cornerstone of diplomatic law. Despite its importance, no complete commentary had been written on the political aspects of the codification process until now. Thus, the original contribution to knowledge of this research is the description of the political aspects of the codification process in general, and the explanation of the British contribution to it in particular. It will be shown that Cold War tensions created the necessary momentum for it to be prioritised in the International Law Commission (ILC) and that procedural rather than substantive issues were the reason for the separate codification of diplomatic and consular relations. Analysing the contribution and role of the British, it will be shown that the British member of the ILC would have favoured codification by passing a UNGA resolution and that the decision to codify diplomatic privileges and immunities by convention led to a change in the British approach. Furthermore, it will be shown that Britain provided one of the leading delegations at the 1961 Vienna Conference. However, despite its leadership role, it could not avoid the inclusion of what, in British eyes, were unfavourable restrictions on the freedom to appoint staff and the freedom of communication. In comparison to traditional British diplomatic practice, codification via the VCDR led to a decrease of diplomatic immunities, while it increased diplomatic privileges. Thus, the ratification of the VCDR implied fiscal concessions on part of the Treasury, and this led to an interdepartmental dispute (i.e. over tax-free reimport of Scotch whisky) which, together with the low legislative priority given to the legislation necessary for the implementation of the Convention, delayed British ratification until 1964.