The Italian steered the seven-year-old to victory in the Stewards' Cup at Glorious Goodwood and asked for the ride in this race before the entries came out.
Ivory was happy to oblige and reports Lancelot Du Lac to be in good shape, having only run at York on Sunday when he was below par on what was tacky ground.
Lancelot Du Lac will have to defy the welter burden of 9st 10lb if he is to become the first horse since Lochsong in 1992 to win the Stewards' Cup and Portland in the same season.
"The ground at York was very tacky in the end, so the race was never run to suit him. He didn't quite get home over the six, but I think this trip and everything will suit him" said Ivory.
"He comes there in great form. Obviously, we've got Frankie, who won the Stewards' Cup on him the last time.
"Frankie was keen to ride him before he was even entered so that's all very positive, but he has got a lot of weight."
Ivory also saddles Stake Acclaim, who has had a well-earned break since running three times last month.
"He's in great form. I was a bit harsh with the poor little fella, running him three times in about three weeks, but he never let me down at all. To him, it probably feels like he's had six months off," said the Radlett trainer.
"He is bucking and kicking at home. The trip and everything should all suit him.
"I'm very happy with both horses."
Captain Colby bids to be the first multiple winner since hat-trick scorer Halmahera, successful from 2002-4, but he has been out of sorts since finishing second to Tupi in the Cammidge Trophy at Doncaster.
Walker has his fingers crossed the horse's liking for the track will bring about a revival.
"He's not in the same form as last year. We're just scratching our heads with him," said the Newmarket trainer.
"He seems to have fallen out of love with the game. We're chancing our arm. He seems to like Doncaster, so let's hope he just bounces back to some kind of form.
"He's good enough to win it, but he just seems to have lost his love for the game."
Justanotherbottle won over this five and a half furlongs in July and ran well when fourth at York on his latest start.
"He's in good form and he's won over the five and a half here before, so obviously the trip's fine," said trainer Declan Carroll.
"He should like the ground. He won with cut in the ground earlier in the season and ran a good race at York last time out.
"I'm looking forward to running him. He's been training well, he's in good nick."
Henry Candy has a fancied contender in Vibrant Chords, who looked as though he would relish the extra half-furlong after putting in good late work to finish second to Desert Law over the minimum distance on this course four weeks ago.
"He'll cope with the ground, I think,and it's a distance that will suit him," said Candy.
"He's in good form so I'd hope he'd do well. His draw (eight) gives him enough options."
Paul D'Arcy feels Spring Loaded will much prefer the straight course at Doncaster, rather than the tight turns of Chester, where he was third from a high draw two weeks ago.
D'Arcy said: "I think at Chester, drawn nine, he was all pushed to be placed. He ran very well, I thought. He could never get in and was always five wide.
"The only downside is this race is over five and a half furlongs. If it was over six, I'd be more confident."