By Harry Allwood

Aidan O'Brien reached a world record 26 Group One winners in a year at Doncaster on Saturday. Here are the horses who have helped him to rewrite the record books.

Horse: WINTER

Age/Breeding: 3yo gr filly; Galileo/Laddies Poker Two

Group One races: 6. Wins: 4. The grey would not have been an obvious one to spearhead O'Brien's assault on Bobby Frankel's record - he did not even train her as a two-year-old - but she developed into one of the season's most prolific performers at the highest level, completing the English/Irish 1,000 Guineas double before winning the Coronation Stakes and the Nassau.

Her winning sequence came to an end in the Matron Stakes, when touched off by stablemate Hydrangea, before finishing a never nearer ninth in the Arc. She did not run again but the consistent filly more than did her bit.

Horse: ROLY POLY

Age/Breeding: 3yo bay filly; War Front/Misty For Me

Group One races: 7. Wins: 3.

Suspicions that Roly Poly might be "just a two-year-old" seemed likely to be accurate when she was well held on her first two starts this term. She flourished as the season unfolded, however, and won the Falmouth Stakes, Prix Rothschild and the Kingdom Of Bahrain Sun Chariot Stakes.

She was also runner-up to stablemate Winter in the Irish 1,000 Guineas and the Coronation Stakes and she may not be finished yet, with the Breeders' Cup on her agenda.

Horse: CHURCHILL

Age/Breeding: 3yo bay colt; Galileo/ Meow

Group One races: 6. Wins: 2.

Churchill was Europe’s champion two-year-old in 2016 and got O’Brien off to a flying start this year when he became the ninth horse to complete the English/Irish 2,000 Guineas double.

It looked like he might dominate for the summer but there were no more Group One wins left in his cupboard. He was placed in two Group One’s thereafter, most notably when runner-up to Ulysses in the Juddmonte International Stakes at York in August. He is an intended runner in the Breeders’ Cup Classic.

Horse: HIGHLAND REEL

Age/Breeding: 5yo bay horse; Galileo/Hveger

Group One races: 4. Wins: 2.

One of the few older horses who have stayed in training with O’Brien, Highland Reel began the season with an all-the-way victory in the Coronation Cup in June before gaining his first Royal Ascot success in the Prince Of Wales’s Stakes later that month.

The stalwart has now won over £6m in prize money, more than any horse O’Brien has trained, and that amount may increase next month as O’Brien has confirmed the globetrotter will bid for back-to-back wins in the Breeders’ Cup Turf which he is the general 9-4 favourite.

Horse: CAPRI

Age/Breeding: 3yo grey colt; Galileo/Dialafara

Group One races: 4. Wins: 2.

The grey would not have been considered by many to become a two-time Classic winner this season. He struggled to land a blow when sixth in the Derby at Epsom but showed huge improvement to defeat Cracksman and Wings Of Eagles in the Irish version a month later.

He then justified favouritism in a compelling St Leger to give O’Brien his fifth win in the race as well as taking O’Brien’s Group One tally to 18. Capri disappointed on his latest outing, when he beat only one horse home in the Arc, but has more than played his part.

Horse: HAPPILY

Age/Breeding: 2yo bay filly; Galileo/You’resothrilling

Group One races: 2. Wins: 2.

A winner of four of her six starts, Happily gained her first Group One success when she led home a one-two-three for O’Brien in the Moyglare Stud Stakes. She then followed up that success when she beat the colts in the Prix Jean-Luc Lagardere on Arc day.

She may bid for her third Group One win in succession next month as O’Brien has suggested she is a possible runner in the Breeders’ Cup Juvenile Fillies’ Turf.

Horse: U S NAVY FLAG

Age/Breeding: 2yo bay/brown colt; War Front/Misty For Me

Group One races: 3. Wins: 2.

The progressive U S Navy Flag has had a busy two-year-old campaign, having run ten times and recorded back-to-back Group One wins on his last two starts.

He caused a minor upset when he defeated stablemate Fleet Review in the Middle Park Stakes and led home a staggering one-two-three-four for O’Brien in the Darley Dewhurst Stakes.

U S Navy Flag may not be finished yet, with a tilt at the Breeders’ Cup Juvenile Turf a possibility. He is the general 3-1 favourite.

Horse: HYDRANGEA

Age/Breeding: 3yo bay filly; Galileo/Beauty Is Truth

Group One races: 7. Wins: 2.

The consistent Hydrangea has had a busy campaign, running eight times. She finished behind Winter in four consecutive Group One races before she caused an upset when defeating her in the Matron Stakes.

She finished a close second behind stablemate Rhododendron in the Prix de l’Opera before she showed a tremendous attitude to defeat Bateel in the Fillies & Mares on Champions Day to give O’Brien his 25th Group One winner and equal Bobby Frankel’s record.

Horse: WINGS OF EAGLES

Age/Breeding: 3yo bay colt; Pour Moi/Ysoldina

Group One races: 2. Wins: 1

Wings Of Eagles was not classed as one of O’Brien’s superstars as a two-year-old but showed what he was capable of when he caused one of the shocks of the season in the Derby - finishing with a flourish to overhaul stablemate Cliffs Of Moher late on at 40-1.

He then went on to finish a close-up third behind Capri and Cracksman in the Irish Derby but sadly it proved to be his final appearance as he suffered a career-ending injury during the race.

Horse: CARAVAGGIO

Age/Breeding: 3yo grey colt; Scat Daddy/Mekko Hokte

Group One races: 4. Wins: 1

One of the disappointments of the O’Brien season? The horse labelled “the fastest horse we’ve ever had”, was unbeaten in his first six starts and defeated Harry Angel in the Commonwealth Cup.

However, he has not turned into the sprinting superstar that many imagined and three subsequent Group One runs failed to yield a victory.

He ended his campaign when third in the Sprint Stakes at Ascot and is now heading for stud.

Horse: SIOUX NATION

Age/Breeding: 2yo bay colt; Scat Daddy/Dream The Blues

Group One races: 2. Wins: 1.

The colt was a surprise winner of the Group Two Norfolk Stakes at Royal Ascot before he took the step up in class in his stride to win the Phoenix Stakes.

“He travels very well and quickens very well - even though he's a big horse, he's got a lot of speed,” O’Brien said. Sioux Nation disappointed when sixth behind U S Navy Flag in the Middle Park Stakes on his final start this season.

Horse: ORDER OF ST GEORGE

Age/Breeding: 5yo bay horse; Galileo/Another Storm

Group One races: 3. Wins: 1.

A winner of half of his 22 starts, the admirable Order Of St George stormed home to win the Irish St Leger for the second time and provided O’Brien with his fourth win in the race.

He was unlucky not to record a Group One victory earlier in the season when he finished a short head behind Big Orange in the Gold Cup at Ascot as he was arguably left too much to do.

Horse: CLEMMIE

Age/Breeding: 2yo bay filly; Galileo/Meow

Group One races: 1. Wins: 1.

Clemmie, a sister of dual Guineas hero Churchill, marked herself as a filly with a big future when she broke the track record in the Group Two Duchess Of Cambridge Stakes at Newmarket. She then went on to win the Cheveley Park in great style at the main expense of Royal Ascot winner Different League.

After the race, O’Brien said: "She's a lot like Churchill, she's right in his mould. She's got a great mind, plenty of speed, stays well and nothing fazes her so she's a filly to look forward to.”

Horse: RHODODENDRON

Age/Breeding: 3yo bay filly; Galileo/Halfway To Heaven

Group One races: 5. Wins: 1.

Rhododendron would have finished closer to Winter in the 1,000 Guineas had she enjoyed a clear passage but finished two lengths adrift of her stablemate.

Things did not go to plan for the filly in three Group One races afterwards but she gained a deserved success in the Prix de l'Opera when she beat stablemate Hydrangea by a head.

She may yet gain another Group One for O’Brien as she is the general 5-2 favourite for the Breeders’ Cup Filly & Mare Turf.

Horse: SAXON WARRIOR

Age/Breeding: 2yo bay colt; Deep Impact/Maybe

Group One races: 1. Wins: 1.

The unbeaten colt confirmed himself a top-class prospect when giving O’Brien an eight Racing Post Trophy winner. In the process, of course, he also gave the trainer his record-breaking 26th Group One success.

Inside the final furlong it looked like Roaring Lion had his measure, but the 13-8 favourite rallied tenaciously to land the spoils.