Craig Williams rode the mare Southern Speed to a comfortable win yesterday in the $2.5 million dollar feature Caulfield Cup race.

It was co-trainers Leon Macdonald and Andrew Gluyas first Caulfield Cup win, with Southern Speed's first win beyond a 1400m race.

"Just sensational," an elated Macdonald said.

"As soon as she got to a mile(1600m)-plus (this campaign), she's showed her form.

"She's very sound, she hasn't had a problem.

"She's not in the Melbourne Cup, we've done our job."

It was Southern Speed's fourth career win and she has also recorded three placings for prize money in excess of $1.85 million.

Williams was as rapt in the performance as Macdonald.

"Leon's done a great job," he said.

"He said 'Just go out and win, and win easy'.

"At the end she ran away (from them).

"She was just dominant".