Rebecca Colley, aged 18, and Millie – who competes as Doodle Daydream – took top spot in the national Open Junior Agility Championship in Moulton, Northamptonshire.
They beat a strong field to record the quickest time with the fewest faults over a complex course of jumps, weaves, tunnels and platforms.
Rebecca said: “Millie did really well, everything I asked of her. It was quite nerve-wracking, but once we got out on the course she was really good and focused. It was still a huge surprise to win. I was not expecting it at all.”
Their victory is the latest in a run which includes a junior Crufts title in 2017, and two podium places this year.
They have also been selected for the adult Team GB squad, putting them in with a chance of going to the European and World Championships later this year.
Rebecca said: “Now I’m in the adult category, it’s very competitive with much more experienced handlers.”
Rebecca only began training four years ago with the North Derbyshire Dog Agility Club – with whom they also compete in team relay events.
Rebecca said: “It started when Millie was a puppy. We went somewhere with a £1 have-a-go agility course and tried it out for fun.
“She loved it, so we started taking lessons.
“The club has been great, and really supported us every step of the way. I’m really grateful to them, and to my parents for driving us around.
“Millie is really eager to learn and loves doing it, which helps a lot. Some dogs just have a natural drive for it, and that’s the most enjoyable part of all: seeing Millie have a good time. She always has a smile on her face when she comes out of the ring.”
The pair train or compete most weekends, with Rebecca fitting it in around her final year A-level studies at the Outwood Post-16 Centre.
Rebecca is considering a career as a dog trainer, and has just taken on a second puppy, Swift, who she hopes will follow Millie’s example.