Oliver was one of several British RBMU missionaries called up in 1940 and appointed as lieutenants in the Indian Army, at that time still led by the British.
Under Oliver's leadership RBMU set up a hospital in the Muzaffarpur Leprosarium, which had hitherto only provided a home to those excluded from their society because of leprosy.
One of the leaders of the revolt had been treated at the RBMU mission hospital in Raxaul, and he was well disposed toward the possibility of Christians being allowed to work in Nepal.
In 1961, at the invitation of the RBMU Board of Directors, Oliver returned to London to take up the newly created post of executive secretary.
Concurrent with his appointment as executive secretary of RBMU, Oliver joined the Committee of Management of the Evangelical Missionary Alliance, which had been created in 1958.
He had already approached Oliver about the possibility of being seconded part-time from RBMU to replace him within the EMA.
During 1974, in his capacity as executive secretary of RBMU, Oliver returned to Nepal to participate in the celebrations of the twentieth anniversary of UMN's work.
In 1976 Oliver retired from his role in RBMU. At an age when most people's thoughts turn to retirement activities, Oliver not only remained as general secretary of the EMA but also became an associate director of Tearfund, an autonomous relief agency that was founded in 1968 as the Evangelical Alliance Relief Fund, on whose board Oliver served since its inception.