Endgame riddle: Tal vs Najdorf, Bled 1961

A strong 20-player round-robin tournament took place in 1961 at the traditional chess city of Bled. Mikhail Tal won the event ahead of a young Bobby Fischer, who impressed with his undefeated performance. In the final round, Tal converted an endgame with rook and bishop against rook and knight in his game against Miguel Najdorf. But was the endgame winning all along? Or could have Najdorf held a draw? Help GM Karsten Müller find the answer to these questions!