Question: What is the name of the Grand Duke of Lithuania, then the King of Poland, who reserved the rights of the overlord under the Pact of Vilnius and Radom?
Sentence (from "Pact of Vilnius and Radom"): Vytautas, Grand Duke of Lithuania, became fully in charge of the Lithuanian affairs, while Władysław II Jagiełło, King of Poland, reserved the rights of an overlord.
Relevant evidence: Yes