It was a fantastic feat on the part of the Rosewell House maestro, considering the daughter of Marju began her season in a lowly maiden at Limerick.
She improved dramatically to take a Group 3 at Leopardstown, but to then step up to Group 1 company and land a classic is testament to the skills of the legendary handler.
“She improved from Leopardstown and has just got better with every race,” said Weld. “A lot of work went into the filly over the winter, especially giving her confidence going into the stalls.
“I can see her stepping up in trip, but one day at a time, today was the day. I will talk to Sheikh Hamdan (owner) and Angus Gold (racing manager) before making plans.
“I am delighted to train my first classic winner for Sheikh Hamdan, he has been a great supporter of mine over the years.”'
The Godolphin horse, Anna Salai, was in front over a furlong out, looking the most likely winner.
But Pat Smullen had Bethrah in full flow and she answered his driving to grab the leader close home and score by a head.
Mick Channon's Music Show was only a neck away in third, with the Ballydoyle pair, Remember When and Lillie Langtry, right on top of them.
Weld had previouly won the race with Prince’s Polly in ’82, Trusted Partner in ’88 and Nightime four years ago.
Pat Smullen, who partnered Nightime, was enjoying his second success in the race and said: “This is not a surprise, we always thought she was a good filly.
“That was a fair performance, because we were stopped once or twice and she got me out of trouble. She surprised me the way she quickened and then quickened again.”
Questioned as to where Bethrah should go next, Smullen responded: “The logical place is the Coronation (Royal Ascot), but that's up to the boss and Sheikh Hamdan.”
Keep Jan Vermeer on your side for the season is surely the message, following his stunning seasonal debut in the Group 3 Airlie Stud Gallinule Stakes. He never left second gear for Johnny Murtagh to totally outclass the field, scoring by an unflattering length and three parts.
Murtagh let out an inch of rein at the furlong pole and the son of Montjeu quickened away in the style of a high-class horse.
“I’m delighted, he was just ready to come racing,” said Aidan O’Brien. “He has loads of class and should come on a good bit for this.
“He has the option now of Epsom or the French Derby and, hopefully, will go for one of them.
“We'll talk to the lads (owners) and to Johnny as well. The four big horses are Jan Vermeer, St Nicholas Abbey, Midas Touch and Cape Blanco. In an ideal world you would like to divide them up.”
William Hill kept St Nicholas Abbey as their 7-4 favourite for the Epsom Derby, with Jan Vermeer thumped in from 16-1 to 6’s.
Ladbrokes now offer St Nicholas Abbey at 2-1 and have Jan Vermeer as clear second favourite, 5-1 from 12-1.
O’Brien and Murtagh teamed up to land their first Group 1 of the campaign when Fame And Glory produced a smashing performance to take the Tattersalls Gold Cup by seven lengths.
He cantered past stable companion, Dixie Music, over two furlongs from home and then surged on to easily beat Recharge.
Fame And Glory was backed as if defeat was out of the question in the ring, finding 8-15 from 8-11.
“He is coming forward, that’s what we always felt he could do,” reported O’Brien. “He’s really there now.
“He’s an exciting horse and, though it is a quick bounce-back, could go for the Coronation Cup (Epsom).”
Murtagh and O'Brien completed a treble when Bright Horizon, backed from 4-1 to 9-4, swept through late to grab the Kilsaran Lifestyle Maiden.
“Johnny gave him a great ride and it looks like he will stay further,” remarked O'Brien.
Dermot Weld’s newcomer, Moonlit Garden, was an easy to back 10-1 shot in the Yas EBF Maiden, but belied the apparent lack of confidence with a clear-cut victory.
Perfectly drawn against the rails, the daughter of Exceed And Excel travelled like a dream through the contest.
Pat Smullen allowed her lead well over a furlong down and she lengthened to score by three lengths.
“She was working very nicely and will go for the Queen Mary (Royal Ascot),” reported Weld.
“She’s fast and did it impressively. Bobby O'Ryan bought her for me at the Kempton breeze-up sales.”
Padraig Beggy rode a powerful finish to grab the United Arab Emirates Handicap on Donal Kinsella’s Vivacious Vivienne.
Successful previously at Navan, Vivacious Vivienne swept up late to short head the flattering Gimli’s Rock.
The plan for the daughter of Dubai Destination is a mile and a half handicap at Galway on the Friday night.
The biggest lottery of the day, the six furlongs Jondol Furniture Handicap, went the way of Lough Mist.
She was committed by Pat Shanahan fully two furlongs from home and the tactics were spot-on, as Tracey Collins’ four-year-old held on to beat Dash Back.