Southern Speed gave South Australian trainer Leon Macdonald the high point of an already successful career when she beat a high class field in Saturday's $2.5 million Caulfield Cup.Having her first start at 2400 metres, the four-year-old enjoyed a cosy run throughout under Craig Williams after jumping from gate three with Hong Kong horse Mighty High in the lead.Williams extricated Southern Speed ($10) from behind the leaders in the straight and she ran past Green Moon ($11), who had made a light

Southern Speed gave South Australian trainer Leon Macdonald the high point of an already successful career when she beat a high class field in Saturday's $2.5 million Caulfield Cup.

Having her first start at 2400 metres, the four-year-old enjoyed a cosy run throughout under Craig Williams after jumping from gate three with Hong Kong horse Mighty High in the lead.

Williams extricated Southern Speed ($10) from behind the leaders in the straight and she ran past Green Moon ($11), who had made a lightning dash from midfield to hit the front, to score by 1-1/2 lengths with Tullamore ($20) a half-length away third.

"This is sensational. This was really the one that we wanted," said Macdonald who has trained in partnership with his son-in-law Andrew Gluyas in recent years.

Mighty High weakened to finish second last with favourite December Draw behind him.

Macdonald has won 13 Group One races with the likes of Gold Guru, Umrum, Rebel Raider, French Cotton, Minegold and now Southern Speed.

He trained Southern Speed's dam who was placed just once, in a Cheltenham 1000m maiden, from three starts.

"She (Southern Speed) makes mum look a bit silly," Macdonald said of the dam who was raced by Wolf Blass.

Southern Speed, who is raced by a group of six including Macdonald's long time stable client Harry Perks, showed plenty of ability early in her career, winning the Group Three Vanity (1400m) at Flemington at her third start.

"She showed us so much as a late two-year-old that (stable jockey) Clare (Lindop) wanted to run her in the Dermody Stakes, the 1000m race, but it didn't eventuate because she went shin sore," he said.

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

After she was placed in the Group One Australasian Oaks (2008m), Macdonald set the mare for the Caulfield Cup and she is still in next Saturday's $3 million Cox Plate (2040m) at Moonee Valley.

However, the Melbourne Cup was never on the agenda.

"There is a chance she could run in the Cox Plate, especially if you could guarantee me barrier three again," said Macdonald.

Southern Speed didn't do much in her first two runs this preparation but came to life with a third-up fourth to King's Rose in the Stocks Stakes at Moonee Valley before being left in front too early when runner-up to Lion Tamer in the Underwood Stakes (1800m) at Caulfield.

She was bottled up on the fence when working home for a solid fourth to December Draw in the Turnbull Stakes (2000m) at Flemington.

If there was a tinge of disappointment for Macdonald it was that Lindop was sacked from the mare earlier in the spring, with the syndicate eventually settling on Craig Williams who rode the mare for the first time in the Turnbull.

"The saddest moment in the whole thing was that Clare wasn't on the horse," he said.

"She spent a lot of time getting this horse ready and it's just not good."

The big disappointment of the race was $3.30 favourite December Draw who settled eighth early but failed to stay the trip and dropped out to finish last.

A veterinary inspection post race could find nothing abnormal with the gelding.

The Luca Cumani-trained Manighar was fourth and the best of the four internationally trained runners with stablemate Drunken Sailor finishing seventh, Saptapadi 14th and Hong Kong's Mighty High 17th.

Vets found nothing amiss with Mighty High after the race but jockey Darren Beadman was mystified.

Lucas Cranach, who had been under scrutiny with a quarter crack in a hoof, ran well for fifth but the a post race inspection revealed he was slightly lame in the near fore hoof.