power broker

valtahahmo A person or group having the ability to influence important decisions, especially in public policy, politics, and business.
1969 Jan. 3, "http://www.time.com/time/magazine/article/0,9171,900486-3,00.html Men of the Year," Time:

In France, a near-revolution by students and workers came close to toppling Charles de Gaulle in May; its economic aftermath in November almost certainly discredited forever Gaullism's vaunted role as the power broker of Europe.

Gen Ali Murtopo—vice chairman of Indonesia's Supreme Advisory Council, former information minister, a major power broker in and out of the army—declared after a meeting with the president that the killings were justified.

The Qatar government, which runs the QIA, will become a major power-broker in determining the future of the London exchange.