My take on his style is that he regarded the words as supreme. The tune was there to carry the words, and could be pulled about and ornamented as necessary. This seemed to extend to when he sang accompanied - most singers find that imposes some regularity, but Peter seemed to sing in much the same way and his inimitable and distinctive accompaniment followed that.

He had a very individual style, but I think it is perfectly possible to extract the underlying tune from it. The important thing is that it was very effective at getting the song across, albeit not to everyone's taste.

I can't claim to have known him, but I did meet him several times, and once spent several hours in his company. He was charismatic but could be contrary, and I can understand how he rubbed some people up the wrong way. I found him to be an electrifying performer, which somehow his recordings (even the live ones) don't quite capture for me. An extraordinary talent and a great loss.