Boss Lane will make his long-awaited return to racing at Randwick after his previous preparation came to an abrupt halt when tests revealed an elevated cobalt level.

Ron Quinton subsequently escaped a penalty because Racing NSW stewards were satisfied the level was high because the feed the trainer was using contained up to 50 times as much cobalt than disclosed on the label.

Quinton was relieved to put the issue behind him and bring a stable favourite back for Saturday's feature, the Listed Christmas Classic (1200m).

Boss Lane last raced in the Group Two Missile Stakes (1200m) on August 5 before being disqualified from fourth when the cobalt inquiry ended in October.

"He's always been one of the real favourites of the stable. He's won nine races for us, seven at Randwick. He's been a handy horse," Quinton said.

Boss Lane won his black-type debut in the Listed Brian Crowley Stakes (1200m) in 2013 but struggled to step up in class when he ran in the Group One Galaxy and TJ Smth Stakes (1200m) three years later.

Quinton said Boss Lane, who has earned $598,000 prize money from 42 starts, was now best suited to Listed or Group Three company.

"This is about his level because he just struggles when he gets to Group Two. If we can strike a win with him here or there, we're happy," he said.

Quinton has booked Irish jockey Declan McDonogh who will be ridng at his first Saturday metropolitan meeting.

McDonogh has six wins since his Australian debut at Gosford on December 7 including a treble at Newcastle last Saturday.

"He rides well. I didn't hesitate to put him on. He'll get on good with Bossy," Quinton said.

The champion jockey-turned-trainer revealed a connection between the pair, who both rode for Irish trainer John Oxx.

Quinton worked for Oxx in the 1980s and rode Petite Ile to win the Irish St Leger in 1989.

"I had three good seasons there and we still keep in touch," he said.

The Bjorn Baker-trained Group One winner Music Magnate is the early favourite ahead of his first start since May.

Music Magnate suffered a fetlock injury but has shown his fitness with wins in two recent barrier trials.