The Philip Hobbs-trained grey took his winning sequence over timber to six when holding a determined late rally from Hardy Eustace to land the boylesports.com International at the same track on Saturday.
Richard Johnson made most of the running on Warner’s charge, who kicked clear heading down the hill for a one-length victory, and is now the 5-2 favourite with Ladbrokes for the Champion Hurdle, although Coral still offer 7-2.
Warner said: “I spoke to Philip this morning and hasn’t lost much weight; he’s only lost about half of what you would normally expect a horse to lose.
“We are very pleased with how he took the race as he came home last night and ate up brilliantly.
“He is a very big horse and is very sound at the moment, so I am keen not to over-race him.
“I had a long chat with Philip and there are several opportunities for him, but I think he will have just one race before Cheltenham in the Agfa Hurdle at Sandown at the beginning of February.
“He is a good eater so puts on weight and for that reason he could have two races, but he is only a four-year-old and he hopefully has a long future ahead.
“The Agfa falls at about the right time. It is a nice race to win and the track is a bit like Cheltenham with a stiff finish.”
Detroit City’s jumping was sloppy in the early part of Saturday’s race, and Warner continued: “The sun affected his jumping early on but when they quickened his jumping was much better.
“Richard said he was idling in front too and he had plenty left in the tank.
“He quickened well and that is his Flat class showing — don’t forget he did win a Cesarewitch.
“Yesterday was his first real test of character and he has done it nicely.”
And Warner fired a warning shot to Detroit City’s rivals, including reigning champion Brave Inca, when adding: “He keeps improving and there are still three months to Cheltenham.
“He defied the statistics when he won at Aintree last year, he broke the track record at Cheltenham and he keeps doing everything right.
“I hope he will go on to run well at Cheltenham — where I think you need a two-and-a-half-mile horse to win the Champion Hurdle.
“He will then go to Aintree and run over two and a half miles, which is what people keep telling me he needs.”
Meanwhile Totesport Cheltenham Gold Cup third Forget The Past will be trained for the John Smith’s Grand National in April – if he recovers from a back problem in time.
Last season’s winner of the Red Mills and Bobby Jo Chases went on to chase home War Of Attrition at the Festival in March, but has not been seen since disappointing behind Mouse Morris’s charge a month later.
His trainer Michael O’Brien this weekend revealed the eight-year-old has suffered a setback, but hopes to get him back on track with an assault on the Aintree showpiece in mind.
“He has been having treatment on a back problem,” said O’Brien.
“Two of his vertebrae have been rubbing together. We think it could have happened early in the year during a schooling mishap on the Curragh.
“If the treatment works he will reappear at Leopardstown over Christmas and he will then be trained with the Grand National in mind.
“If he isn’t right then we will give the rest of this season a miss.”
O’Brien was on the mark with Gold Cup aspirant In Compliance at Punchestown on Sunday, and added: “Forget The Past doesn’t have pace, he’s just a big bulbous horse that gallops along and he doesn’t have the speed of In Compliance.”