"He had a wide draw, and he (Williams) elected very quickly, which he said to me he might, to come in midfield and then he got caught in a pocket.
"Any lesser jockey would not have got out of, but the waters opened, and he went boom. That was the exciting part, the boom."
Williams described Sir Delius a 'great horse', and it was exciting people were getting behind him.
He said Waterhouse and Bott had given him the confidence that Sir Delius could overcome the wide draw.
"In Group 1 races, you don't think you can win like that, but we were very confident he could do it," Williams said.
"We had the outside barrier draw. Gai and Adrian were very good about having an open book without too much pressure about riding him.
"I had to use a few carrots to find a spot, but when the chips are down, this horse is a winner."
Williams is unsure what distance range Sir Delius can extend to, but feels the Melbourne Cup, with 55.5kg, is worth taking a punt on.
"I just said you will never have 55-½ kilos in the Melbourne Cup again," Williams said.
"I worked him during the week at Flemington, and he walked out and he owned the track.
"He owns everything he does and today you saw that attitude. He puts the writing on the wall when under pressure against these top horses, and he's delivering."