Harrop served for 39 years as a Foreign Service Officer, with postings as United States ambassador to Guinea, Kenya and the Seychelles, the Congo (Kinshasa), and Israel.

At age ten, he moved with his family to New Brunswick, New Jersey, where his father, a research physician, worked for E. R. Squibb & Sons.

At the invitation of Frank Boyden, the headmaster of Deerfield Academy, Harrop spent about five months teaching at the school before entering the Marine Corps, in which he served during the Korean War.

One of Harrop's sons was born the day before he left for Italy for his first assignment, at the U.S. consulate general in Palermo, Sicily in 1953.

He helped administer the Refugee Relief Program on the island, where at the time the Mafia held great sway.

[1] Harrop served in Palermo from 1954 to October 1955, when he was transferred to the U.S. Embassy in Rome to be assistant commercial attaché there under Ambassador Clare Boothe Luce and, later, James David Zellerbach.

In Brussels, Harrop served under ambassadors Douglas MacArthur II and later Ridgway Knight; he continued to follow African matters and did work relating to Belgian commerce.

In 1966, Harrop left Brussels and went to the Congo, spent two years as principal officer at the U.S. consulate in Lubumbashi (the name of which had recently changed from Elisabethville).

The region was extremely dangerous at the time; Harrop would arrange for C-130s to be flown down to Katanga during the period of greatest tension.

In 1968, Harrop left the Congo after being assigned to do graduate work for a year at the Woodrow Wilson School of Public and International Affairs at Princeton University as part of a "Mid Career Program" sabbatical.

[2] As ambassador in Conakry, Guinea, Harrop faced hostility from President Ahmed Sékou Touré, leader of a radical, pan-Africanist movement.

Key issues handled during Harrop's tenure in Conakry were Soviet overflights and bases in the country and U.S. humanitarian aid in Guinea.

Key issues dealt with by Harrop in this position include the application of the Foreign Corrupt Practices Act to U.S. commercial ventures in Kenya; the use of Kenyan coasts by U.S. Navy ships; territorial disputes between Kenya and Somalia, Ethiopia, Uganda, and Tanzania; and human rights in the country.

[1] Harrop returned to Washington to become Inspector General of the Department of State and the Foreign Service, serving from December 12, 1983, to August 27, 1986.

In 1982 the GAO has issued a report pointing out that an Inspector General who was a Foreign Service officer seeking an onward assignment and who was, like Harrop, a key participant in management decisions lacked the requisite independence to meet US Government standards to conduct audits and investigations.

[2] Important events during Harrop's tenure included the Dotan affair, the recognition of the PLO by Israel for the first time, and the beginning of the talks that led to the Oslo I Accord.

[1] In 2004, Harrop was among 27 retired diplomats and military commanders who publicly said the administration of President George W. Bush did not understand the world and was unable to handle "in either style or substance" the responsibilities of global leadership.