WHY WAS LORD CARRINGTON APPOINTED EU PEACE NEGOTIATOR IN THE YUGOSLAVIA CIVIL WAR?

I'm watching a BBC doc on the break up of Yugoslavia.

It appears that a civil war was engineered between Serbia and Croatia. The EU appointed Lord Carrington to negotiate for peace. Carrington called for a peace conference between all members of Yugoslavia, and published a peace plan. All members of Yugoslavia attended the conference. But on the day of the conference an extra point was sneakily added to the plan: that all members of Yugoslavia should become independent! This caused outrage and torpedoed any chance for peace.

Thus began the collapse of Yugoslavia, resulting in the wars in 1990s.

But Carrington had already been Sec Gen of NATO between 1984 and 1988, so he was not the independent that was required for peace.

So why was Carrington appointed peace negotiator? And how?