Donnacha O'Brien was officially crowned Irish champion Flat jockey for the second time on the final day of the season at Naas.

The defending champion began the afternoon with a tally of 110 winners for the campaign - giving him an unassailable lead of seven over the 2017 champion jockey Colin Keane, who had a book of six rides.

It has been a titanic battle between the pair for much of the year - before O'Brien pulled clear in the final weeks - and they fittingly fought out a thrilling finish to the Irish Stallion Farms EBF Maiden on the last day.

Nobel Prize and Chiricahua were the 6-4 joint-favourites under O'Brien and Keane respectively, and it was the former who claimed top honours by just a head.

O'Brien's title race victory means he matches the feat of his older brother Joseph, who won back-to-back championships in in 2012 and 2013.

Yesterday, Joseph became the youngest trainer to saddle a Breeders' Cup winner when Iridessa stormed home in the Filly & Mare Turf at Santa Anita.

Donnacha O'Brien said: "It's a relief to win it and to have it over and done. It's head-frying (going for the jockeys' championship), and I don't know how lads like AP (McCoy) and Pat (Smullen) kept going for so many years. It drains you doing it one or two years, so I can only imagine what they went through.

"Colin (Keane) is someone I have the utmost respect for, and to ride over 100 winners in a season not riding for dad (Aidan O'Brien) or Joseph is incredible. It's a true test of how good he is.

"I have been getting unbelievable support from the Magnier, Smith and Tabor families - and I owe everything to them and dad. To be able to ride so many good horses is a real privilege.

"I'm going on holidays tomorrow morning, so I'm looking forward to that. Everyone seems to want me to retire, but we'll think about that on another day."

Joseph O'Brien yesterday became the youngest trainer to saddle a Breeders' Cup winner

While O'Brien already had his championship sewn up before the final day, there was a thrilling climax in the race to be crowned champion apprentice - with Oisin Orr riding a double to ensure he shared the spoils with Andrew Slattery.

Slattery led Orr by 43 winners to 41 at start of play - and Orr came mighty close to closing the gap to one in the opening six-furlong maiden when beaten just a nose on Dermot Weld's Soul Seeker.

However, Orr did strike gold in the following five-furlong handicap on Eddie Lynam's 13-2 favourite Tide Of Time - and then drew level for a share of the title in the concluding P And T Stapleton Ltd Sobac Soil Maiden, with victory aboard the Weld-trained Maria Christina (9-2).

Orr was claiming the title for the second time, having also been champion apprentice in 2017.

He said: "I rode her (Maria Christina) in a schooling race the other day, and she went fairly well, so I had good confidence coming in here.

"You just have to keep going after results like the one in the first race. It was going to be a great season no matter what and it's the most winners I've had in a year. It was nice to get that one in the last race."

Weld added: "I was delighted that they both tied for it. Andy has ridden plenty of big winners for me, but I really wanted Oisin to tie with him.

"The standard of young riders we have in Ireland at the moment is superb."

Aidan O'Brien - father of Joseph and Donnacha - was confirmed as Ireland's champion Flat trainer for a remarkable 22nd time.

The master of Ballydoyle first claimed the title in 1997 - and while Dermot Weld reclaimed the crown the following year, O'Brien has been champion trainer in every season since 1999.

This time, he has trained 118 winners for almost €7.8m in prize money.