The filly heads to Doncaster after a late change of plan by Gosden and the composer Andrew Lloyd Webber, who owns the big race favourite with his wife Madeleine.
Victory for Frankie Dettori’s mount would virtually seal a third trainer’s title for Gosden, whose Roaring Lion heads the field for tonight’s Irish Champion Stakes in Ireland.
The 67-year-old has enjoyed a long association with the Lloyd Webber family. He trained the St Leger favourite’s dam, Dar Re Mi, and, more recently, trained The Fugue to multiple successes for his high-profile owners.
Unraced last year, Lah Ti Dar hit all the right notes when winning at Newbury and Newmarket earlier this year before sickness forced her to miss the Epsom Oaks and other big races.
However, she made a winning return at York’s Ebor festival – her 10-length win in the Galtres Stakes could not have been more impressive – and connections opted for this Classic in favour of tomorrow’s Prix Vermeille at Longchamp.
“Frankie was adamant she should run in the St Leger when he got off her at York and often the feel a jockey gets when they immediately get off a horse is the one to listen to,” said Gosden, who is seeking his fifth win in the iconic one-and-three-quarter mile race.
“He said she could have kept going another three furlongs and she certainly stays well.
“We ummed and aahed about running her in the Yorkshire Oaks, instead of the Galtres on the same day, but thought she’s been off a long time and been sick, so don’t throw her in a Group One.
“Instead of having a hard race, she had a lovely extended hand ride gallop. I had no doubt about her level of fitness, but when they’ve been sick like that you worry.
“It was a strange sort of viral thing. Nothing else in the place had it – her bloods were all wrong and she was very down in herself.
“The great thing is that the one day she showed it to us she’d only done a gentle canter that morning – thank God she hadn’t worked.
“She wasn’t right that afternoon – she had a temperature and we stopped. To that extent you are always terrified about doing some damage to a horse if you go and work them and then they are not right the next day, but luckily she had all the rest and all the time she needed.
“She missed a long, hot summer and so she’s a fresh filly for the autumn with plenty of ability.”
Lah Ti Dar’s chief rival appears to be Kew Gardens, one of five runners for five-time St Leger-winning trainer Aidan O’Brien.
The Galileo colt won the Queen’s Vase at Royal Ascot and the Grand Prix de Paris during the summer before finishing third under a Group One penalty in last month’s Great Voltigeur at York to Charlie Appleby’s Old Persian, who reopposes today.
O’Brien said: “I suppose Kew Gardens would be the one (best chance). He is the horse that has already won a Group One and we’ve always loved him. He is a very relaxed horse with a good mind, which always helps.”
Yorkshire hopes rest with Mark Johnston’s Dee Ex Bee as Britain’s trainer with most wins, who is based in Middleham, tries to provide champion jockey Silvestre de Sousa with a first Classic.
Second in the Epsom Derby, Brazilian-born de Sousa, 37, is hopeful that Dee Ex Bee has the class – and stamina – that will be required on Town Moor.
“He is a nice horse to have a ride on and I’m just very pleased to be on the horse,” said the jockey.
“In Classic races if you are not associated with the big yards like John Gosden, Sir Michael Stoute and Aidan O’Brien it is hard to get these big horses that can take you to the top.
“This makes rides like this 100 per cent more important. It’s nice to ride winners day-in, day-out, but it would be nice to get a top horse to take me to the top level. It has been something I’ve been working for. It’s not quite happened but it will be a great achievement.”
Although Dee Ex Bee was beaten last time out at Goodwood, de Sousa added: “It would be my dream come true to win this for Mark Johnston. He he has been very good to me for years and this would be a good way to say thank you for that support. I will be giving him the best ride I can.”