Joseph O'Brien feels Leading Light makes his job look easy as the colt attempts to maintain his unbeaten run this season in the Palmerstown House Estate Irish St Leger at the Curragh today.

The four-year-old, who won the Ladbrokes St Leger at Doncaster last year, stepped up to take the Ascot Gold Cup in June but showed he still had the pace to win over shorter distances when claiming a trial for this race over the mile-and-three-quarters trip last month.

In 10 career races he has only lost twice - on his debut and in the Prix de l'Arc de Triomphe last October - and will be a red-hot favourite to give Aidan O'Brien his first win in the race since Septimus in 2008.

"He seems to have come out of his prep race at the Curragh really well. He idled in front that day but always does and won nicely. Ground or trip is not a massive problem for him. He is an uncomplicated horse and I can ride him handy or take my time and that makes my job very easy," said Joseph O'Brien.

Leading Light had Royal Diamond back in second in the Leger Trial on August 24 and Johnny Murtagh's veteran meets his conqueror on 5lb worse terms. Nevertheless, he won the race back in 2012 for Tommy Carmody and also struck at Ascot on Champions Day last season.

"Royal Diamond had a good run in the Leger Trial and I've been happy with him since. He's won the Irish St Leger before and he seems to like the Curragh. We're really looking forward to it," said Murtagh.

Dermot Weld runs Pale Mimosa who arrives on the back on winning the Lonsdale Cup at York.

Her jockey Pat Smullen said: "She's a quickly improving mare, she's lightly raced and I don't think we've seen the best of her yet. Her best run was probably her last start at York so, provided the ground is safe and she's in good form, then I think she goes there with a good chance.

"Leading Light is the one we all have to beat but I think she's an improver."