Who is Joachim Messner from Bel Canto: A Novel and what is their importance?

Joachim Messner is the Swiss Red Cross negotiator who is called in to head the negotiations between the terrorists and the government. He is described as a pale man, who is actually vacationing in the country when the terrorists invade Ruben's home. Messner does not speak Spanish, however, and must rely on Gen to translate.