Happen mowed down Morpho Blue in the opening fillies' maiden at Leopardstown to give apprentice championship leader Shane Crosse another victory.

There was a morning-price gamble on Morpho Blue (8/1 to 4/1) and she set out to make all under Shane Foley.

The pair looked to have seen their 15 rivals off racing to the final furlong, however, Happen began to make headway on the inner.

The War Front filly was fourth at the furlong pole and stayed on strongly to get up in the final strides by a short head at 5/1.

Morpho Blue had to settle for second, a length and a quarter in front of Mallacoota (25/1). Racine the 7/4 favourite, looked a big danger as she made progress on the outer in the final quarter of a mile but her challenge petered out in the final 100 yards and she came home fifth.

Shane Crosse said: “She jumped very well, got a position, and just raced a small bit lazily for me. Once I really got stuck into her she was only really hitting top gear when she got to the line.

“I had my doubts, I thought I was going to get there and then I thought I wasn't. Thankfully she just got her head down so it was great.

“I just have to keep trying to get winners now so they have to try and fight back at me. We've only got a small bit to go so hopefully I can hold on.”

On riding for Aidan O'Brien he said: “I never thought I'd ever have a ride for him never mind ride a winner for him so it's brilliant."

Additional reporting by Gary Carson