Conversation so far:
When was Jan van Eyck a court painter?
In 1425 Jan van Eyck moved to Bruges and came to the attention of Philip the Good. His emergence as a collectable painter generally follows his appointment to Philip's court.
Where was Jan van Eyck a court painter at?
Jan Van Eyck served as official to John of Bavaria-Straubing, ruler of Holland, Hainault and Zeeland.
What did Jan van Eyck do as the court artist?
Jan van Eyck served as court artist and diplomat, and was a senior member of the Tournai painters' guild.
Did Jan van Eyck make good money as a court artist?
A court salary freed Jan van Eyck from commissioned work, and allowed a large degree of artistic freedom.

Question: What did he do as a diplomat?
Self-contained rewrite: What did Jan van Eyck do as a diplomat?