John Tuthill, a committed Europeanist and former head of the Atlantic Institute in Paris and US, was appointed Economic Minister at the French Embassy in 1959. He had previously negotiated with Robert Marjolin regarding US concerns over certain aspects of the Common Market, whereby the US felt that preferential treatment would be given to the Six, particularly with regard to agriculture. Tuthill was of the opinion that an agreement would have to be reached between the Common Market and GATT, to prevent preferential treatment. In June 1959, Tuthill and Monnet had talks on the need for a "new" organisation in which the US could participate actively rather than as an observer as with the OEEC, to deal with economic partnership. In another meeting in Paris, December 1959 with Konrad Adenauer, General de Gaulle, General Eisenhower and Harold MacMillan, Tuthill succeeded in convincing the big four of the need for such a platform for cooperation. However, to Tuthill's disappointment a new organisation wasn't created instead the OEEC, became the basis for the OECD. The OECD had as its starting point an emphasis on economic co-operation and development. Tuthill became the American representative to the OECD, and played an important role as an official in John F. Kennedy's administration in ensuring continued support for European affairs. Tuthill was a strong proponent of the Multilateral Force MLF, an American proposal for giving Europeans a role in nuclear defense, through the creation of joint defense force. In 1962, Tuthill was appointed Ambassador to the US mission in the EEC. In this position he worked hard to gain support for British entry into the Common Market. He was also deeply involved at this time in the so-called "chicken war", when American poultry farmers and policy makers were concerned about the consequences of CAP. Tuthill was a key figure in the compromise solution reached between US and EEC. Tuthill suggested that the matter be brought to GATT arbitration, which the EEC agreed upon. Tuthill also worked hard in promoting Kennedy's trade expansion policy and was directly involved in the Kennedy Round of negotiations on trade in Europe.

The originals are held in various Archives and Presidential Libraries in the USA