The Armstrong formula was introduced in 1984 during a period of relative stability in UN peacekeeping. Vote responsibility for all peacekeeping operations rested with the Foreign and Commonwealth Office (FCO) and money was annually allocated to the FCO in the public expenditure survey to meet these costs. Under the Armstrong formula, in the event of an unforeseen increase that could not be met in-year from within existing funds, and subject to Treasury agreement, the FCO had recourse to Treasury’s central contingency reserve.
Peacekeeping activities increased sharply in the early and mid 1990s, and peace support operations became more complex, requiring a broader range of political, military, development and economic activities. In 2001 two new tri-departmental Conflict Prevention Pools (the Africa and Global Conflict Prevention Pools) were established with strands for both peacekeeping and programme activity. Under current arrangements, the first £374 million of assessed contributions are met by HM Treasury and costs above that are borne by FCO, the Ministry of Defence and the Department for International Development from the Conflict Pools and/or from within departmental expenditure limits.