‘Why not try to be the best in the world, just for the fun of it?’ Art Garfunkel on a rich, restless life – and reconciling with Paul Simon

He taught maths and walked across Europe, trying to leave his demons behind. As he goes back on tour aged 84, the folk-pop legend explains how he came back to singing As Art Garfunkel is keen to point out, “I am a singer – there, use that as the title of your article” – but he…