Britainís role before, during and after the Six Day War was determined by its perceived self interest in the region. These interests were defined by the Foreign Office as safeguarding their share of the oil business, Arab investment in London and access to Arab markets and the East, as well as blocking communist inroads into the region. The British recognized their diminished role in the world and favored stability over change.
Prior to the Six Day War, Britain saw a secure Israel as a source of stability in the Middle East. For this reason the nation was willing to provide Israel some weapons to defend itself. As Prime Minister Harold McMillan stated several years earlier,
We do not give the Israelis arms because they are pro-Western or because we admire their achievement. We give them arms because our interest in the Middle East is to keep the place quiet and to prevent war.
Either an Israeli victory or an Egyptian victory in the conflict spelled trouble for British interests. An Israeli victory would have repercussions because the of Arabs' distaste for Western imperialism and their view that Britain was partial to the Israeli side. Only 11 years earlier, Britain had tried to seize the Suez canal from Egypt by force in collusion with Israel and France after Nasser had nationalized it. But Britain also feared that an Egyptian victory would lead to the fall of regimes supported by the West and endanger the oil supply.
The Israeli victory did exacerbate Britain's declining position in the region, as the defeated Arabs imposed punitive measures on the British economy through oil boycotts and removed funds from British banks.
To protect its interests, especially access to oil, British policymakers decided to adopt a more neutral or pro-Arab stance. The Foreign Office, which had always sympathized with the Arabs became more influential in molding British Middle Eastern policy. On June 21, Foreign Secretary George Brown gave a speech that openly supported the Arabs and demanded Israel return territories won in the war. The 1967 war marked a turning point in relations between Israel and Britain, ending a brief period of close cooperation.
Middle East Review of International Affairs, "Britain and the Occupied Territories after the 1967 War," Moshe Gat, December 2006.