Madonna Plays Let's Make a [Custody] Deal ... In London

4/7/2016 7:18 AM PDT

Madonna flew into London Wednesday, presumably to follow judge's orders and hash out a custody deal with ex-hubby Guy Ritchie.

A judge ordered Madge and Guy -- who have been at war for years over how to raise Rocco -- to come up with a plan on how they will handle custody of the 15-year-old, who now lives with Guy in London.

The judge laid down the law last month, urging them to call a truce for the benefit of the boy. And the judge made it clear ... if they don't come up with a plan, he will. 

No word if she bought 2 return tickets.