The 10-1 chance lined up for the fillies’ Classic having landed just one of her eight races as a two-year-old, although her placed efforts in the Fillies’ Mile and at the Breeders’ Cup in the autumn gave her solid claims on form.
Mother Earth won by a length from Saffron Beach (9-1), trained by Jane Chapple-Hyam, with bargain buy Fev Rover (22-1) a neck further back in third. Santa Barbara, stablemate of the winner, was a nose further back in fourth.
She was giving O’Brien his seventh win in the race - and fifth in the past six runnings - and Dettori his fourth. The latter had previously been successful on Cape Verdi (1998), Kazzia (2002) and Blue Bunting (2011).
Dettori, 50, was capping a wonderful weekend for senior riders in the weighing-room. Only on Saturday, 54-year-old Kevin Manning had landed the 2000 Guineas on Poetic Flare.
Watch a full replay of the QIPCO 1000 Guineas
Dettori’ was becoming the oldest jockey to succeed in the first fillies’ Classic of the season since Charlie Smirke scored on Rose Royale in 1957. Smirke was also aged 50, but just over two months older than Dettori when victorious.
"Fifty years old. Come on the oldies. We can still do it," Dettori said. "Great. It's my 20th Classic, so I' delighted - and in my home town of Newmarket. I’m only 10 behind Lester [Piggott, 30 Classic winners] now so I’ve got plenty of time!
"Aidan gave me a lot of confidence. I rode her cold - she was going to come on good. I followed Ryan (Moore on Santa Barbara) and kicked at the top of the hill. I knew she'd get home, and she did, and I was able to enjoy it.
He added: "I love it. I was a bit deflated yesterday after Battleground (well beaten in the 2000 Guineas) - but when you ride in the Classics for Coolmore, even the second or third string you've got a live chance. In the back of my mind, I thought anything is possible."
O'Brien's three runners in the 2000 Guineas had all failed to figure but normal service was resumed in a renewal where there was no hard-luck stories. The Ballydoyle maestro has now won 39 British Classics, to add to the 45 he has achieved in Ireland.
He said of Mother Earth: “She’s a very good filly and always was. It was unfair to the favourite (Santa Barbara) to come but we had to come with the view to coming back over here for the Oaks.
“Santa Barbara is only a baby and Ryan said that he’d liked to have waited longer but he saw Frankie coming down his outside and he had to come then and she was just green in the dip, but after having one easy run it was a great run."
20 Classics and counting for "overwhelmed" Dettori
Santa Barbara, who lined up having won only a maiden, had been a massive market mover in recent weeks but was easy to back on the day, drifting out to 5-2.
By contrast, Alcohol Free was all the rage in the market and ended up sharing favouritism with her. However, the Cheveley Park and Fred Darling winner could never land a blow and had to settle for a close fifth, beaten about two lengths.
Looking ahead, O'Brien said: "I think Mother Earth will stick to a mile and we’ll step Santa Barbara up in trip – the latter was always going to go to the Oaks next time and this filly was always going to go to the Irish Guineas next. That was the plan.
O'Brien gives his verdict to Tom Stanley
“We won’t go again with Santa Barbara (before the Cazoo Oaks). We felt that she would learn as much coming here as she would for three runs, but it was a risk doing it that she was going to get beaten.
“She’ll be fine, she’s classy and she would have learnt a lot today and she has plenty time to get over that. Ryan was very happy and he said to me that in an ideal world he didn’t want to commit as early.
“But with Frankie coming he had to keep going then and she was a little bit unbalanced going into the dip, which is understandable as we’ve never taken her off the bridle at home. Hopefully she’ll come out of it ok and it will do her good."
Dettori added of Mother Earth: "I think she'll get a mile and a quarter. She's very easy to handle and she's very brave. She's not very big, but she's got a big engine."
Ladbrokes cut Mother Earth to 10-1 (from 20-1) for the Cazoo Oaks, and eased Santa Barbara to 4-1 from 11-4. Saffron Beach is 16-1 from 25-1.
Coolmore partnerships are now the most successful owner of all time in the 1000 Guineas with eight victories. The winners have been Mother Earth (2021), Love (2020), Hermosa (2019), Winter (2017), Minding (2016), Legatissimo (2015), Homecoming Queen (2012) and Virginia Waters (2005).
1 Mother Earth (L Dettori) 10-1
2 Saffron Beach (A Kirby) 9-1
3 Fev Rover (P Hanagan) 22-1
Also: 5-2 Jt Fav Alcohol Free, Santa Barbara 4th
Non Runner: 3
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