[1] He then held positions for Shell in various countries, including Sudan, Libya (when Muammar Gaddafi came to power), Dubai, Turkey and Nigeria (1977).

He came to terms with the African National Congress, and helped fund a training scheme to prepare ANC executives for government.

[1] He became chairman of the committee of managing directors of the Royal Dutch Shell Group in 1992 and stepped off in 1993, leaving the chair to Cor Herkströter.

When Holmes retired in 1993, instead of continuing as a non-executive director in the boards of large corporations, he became president of the Hakluyt Foundation, a new office in charge of providing intelligence for big companies.

[7][8] His publications included Mountains and a monastery (1958), Nigeria, giant of Africa (1985), Turkey, a timeless bridge (1988), Türkye (1988).