DURING MACMILLAN'S second term as Prime Minister, the informal empire continued to exercise an important hold on the minds of policy-makers. Despite strong Treasury pressure, ministers decided to maintain overseas commitments - even at the price of rising defence expenditure. Like most of their predecessors since 1945, they considered it vital to maintain a firm stand in order to secure Britain's oil supplies and its special relationship with the United States as well as international confidence in sterling. The plan to withdraw from south-east Asia (Malaysia) has to be seen in this perspective: it was part of Britain's move towards greater mobility, not an imperial disengagement. Aircraft carriers were to replace land bases. Although the stress was increasingly on non-military measures to preserve British influence and to protect British interests, overseas commitments were still seen as indispensable.