Jason Attard had to become the equine world's answer to Jenny Craig to get Sons Of John ready for spring.

It is usually jockeys who battle weight, but at Sons Of John's portly peak he struggled to show his best.

The 29-year-old trainer believes he has conquered the horse's weight problem as he prepares to tackle the Group Two Tramway Stakes at Randwick (1400m) on Saturday.

After finishing third in last year's Group One Epsom Handicap, Sons Of John went to Melbourne where he was unplaced in the Crystal Mile and Emirates Stakes.

Attard said the horse didn't like travelling and was sent for a spell.

And that's where Sons Of John's problems started.

"He got grossly fat and was just horrendously fat when he came back," Attard said.

Despite three trials, he couldn't get into shape fast enough for his Hawkesbury Cup defence and was sent for a break after finishing fifth in the Scone Gold Cup in May.

"We were just chasing our tails," Attard said.

Rather than risk the horse returning to his bad habits in the paddock, Attard opted for a freshen-up at the stable.

"He stood on the walker and stood here at home," Attard said.

"That way I could keep an eye on what he was getting fed and how much weight he was putting on."

Now with two trials under his belt, including a second to Run To The Rose winner Astern when not extended fully, Attard says Sons Of John is fighting fit ahead of the Tramway.

While Winx will dominate the headlines surrounding Saturday's Chelmsford Stakes meeting, Sons Of John holds the honour of being the last horse to come close to defeating the champion mare.

He was narrowly beaten by Winx in last year's Theo Marks Stakes, her third consecutive win in a streak which has now extended to 10.

"We won't forget that one in a hurry," Attard said.

The pair met again in the Epsom Handicap where Sons Of John added another placing behind Winx to his record.

Sons Of John is one of seven Group One-placed horses nominated for the Tramway, while Gust Of Wind and Le Romain have both won at the top level.

"We're not expecting any miracles or for him to go out and smash them first up," Attard said.

"If he does we'll take it, but seeing him in the first four or five in that field would be awesome."

Attard said Sons Of John was likely to have one run after Saturday on his way to this year's Epsom at Randwick on October 1.