The EEC created a system of agricultural subsidies called the Common Agricultural Policy (CAP). In the 1962 cartoon above, Harold Macmillan looks through the window of the "Restaurant de l'Europe" at the six happy EEC member state leaders being fed thanks to the CAP. British leaders at the time probably felt that the UK was missing out economically because the UK had not joined the European Communities (ECSC, EEC and Euratom) when they were first set up…
Up to the early 1960s, the political, commercial and cultural links to the colonies and former colonies of the UK were still strong; the British government felt that joining the Communities was not indispensable.
Also, European political union - the long-term aim of the Communities - meant surrendering part of the sovereignty of the UK to supranational European institutions; the British government and people were very unwilling to do so (this is still the case today...).
Also, the British government was keen to join a free trade area (i.e. with no internal customs rights), but it wanted national governments to be able to impose their own tariffs with regard to countries outside the Communities (in other words it did not want to join a customs union).
The British government and several other European countries set up a free trade area called the European Free Trade Association (EFTA) as an alternative to the EEC. This was less successful than the common market, and so, in 1961, the Conservative Prime Minister Harold Macmillan asked to join the EEC.
Macmillan stressed the "economic" aspect of the EEC, reassuring Members of the British Parliament that the Treaty of Rome "does not deal with defence (or) foreign policy". He pointed out the "remarkable economic progress" of the EEC member countries. He argued that UK membership would not weaken its relationship with Commonwealth countries, but would be "complementary" to it. He said: "I believe that our right place is in the vanguard of the movement towards the greater unity of the free world, and that we can lead better from within (the EEC) than outside."
In 1963, Charles De Gaulle vetoed British accession to the EEC because he was suspicious of Britain’s Atlanticism (he wanted Europe to become a third superpower, not to be dependent on the USA).
In 1967, when, this time, the Labour Prime Minister Harold Wilson requested to join the EEC, de Gaulle once more refused UK application (cf. de Gaulle's May 1967 press conference at 69:57), for the same reason as in 1963, adding that he considered the UK not ready either economically or even "culturally" to join...
Only after de Gaulle resigned in 1969, did negotiations for British accession to the EEC start, with the support of the new French President Georges Pompidou.
Overcoming significant opposition from part of the British public, the Conservative Prime Minister Edward Heath signed the accession to the EEC in January 1973. Denmark and Ireland also joined and the Europe of the Nine was created.
Edward Heath said the Treaty of Accession in Brussels marked "an end and a beginning" for the UK: an end to the UK’s (economic) isolation from the Continent, and the beginning of EEC membership, which would need "clear thinking and a strong effort of the imagination" by the British. He defended the UK’s strong "national identity" but valued the "common European heritage". He wanted the UK to take a leading role in the EEC and thus "contribute to the universal nature of Europe's responsibilities", namely improving relations with countries dominated by the Soviet Union. Heath hoped for further enlargement, but was worried whether the institutions of the EEC would be able to meet the needs of an enlarged community.