Star sprinter Imperatriz (I Am Invincible) has had her final piece of fast work at The Valley on Monday morning ahead of her autumn return in Saturday’s A$1 million Gr.1 Black Caviar Lightning (1000m).

Trainer Mark Walker was on hand to watch the gallop with in-form stablemate Sans Doute over 800 metres.

The pair clocked 51.72 for the work and their last 400 metres in 23.94.

Walker said despite last Monday’s underwhelming trial, it had always been the plan to bring Imperatriz to The Valley for the workout, where she will race second-up in the Gr.1 William Reid Stakes (1200m) on March 23.

“Get her out of her comfort zone a little bit … horses at their home tracks are a bit laidback sometimes, especially as they get a bit older,” Walker said.

“Trials are different to race day and we’re looking forward to Saturday.

“There was a lot of talk on the weekend Mr Brightside’s jumpouts weren’t that great and look what he did.

“These good horses have checks and balances every week and there’s nothing that’s been out of place.”

Given the warm week of weather in Melbourne, Walker said Imperatriz had extra fans installed in her box to cope with the heat.

“She’ll be virtually the identical weight Saturday to what she won first-up in the spring,” Walker said of her condition.

“We think she’s pretty ready … they don’t give Group 1s away so you have to have them pretty ready.”

Imperatriz is $1.75 with Sportsbet ahead of Private Eye and I Am Unstoppable.

Gallop partner Sans Doute, who has won her past two starts at Flemington, will return to Headquarters on March 2.