The handler has had a relatively quiet few seasons after bursting onto the scene when taking over from her father, but there had been green shoots of recovery in recent weeks before this notable triumph.
Happy Diva was still travelling well within herself in the race last year when she was brought down at the fourth last, but she has rarely run a bad race since.
She could be spotted cutting every corner on the inside, just like 12 months ago, but this time she enjoyed a clear path and coming down the hill for the final time, conditional rider Richard Patrick moved her up alongside long-time leader Warthog.
As Warthog faded, Brelan D’As emerged as the final challenger, but a good leap at the last from Happy Diva gave her just enough of an advantage to enable her to hold on up the hill by a diminishing neck.
Warthog was third with Belami Des Pictons, who was hampered early, in fourth.
Lee said: “They are the most fantastic, loyal owners (Will Roseff and family) and it means so much to come and win on the big day for them. When they have a good day, they celebrate and when they have a bad one, they say there is always another one.
“Richard has ridden her through her entire chase career and he rides her a home at lot. Jordan Devlin has done all the work on her and we knew she would come on for Wetherby, but we didn’t think she would come on quite this much.
“With a circuit to go, I thought Richard had her absolutely perfectly positioned and I couldn’t have been happier to be honest.
“You don’t get too carried away with a horse like that as you know what is round the corner sometimes.
“Richard has been with me three years now. He came on as a conditional and he is a very good, balanced rider and he is excellent on the big stage. Nerves don’t matter to him, unlike me.
“We got done in the Grand Annual by a horse owned by Mr (JP) McManus (owner of Brelan D’As) and I was pleased to reverse the placings in that respect. Hopefully he might send me a horse now.”
Paul Nicholls was satisfied with the Brelan D’As’ effort in second place.
He said: “In my mind I knew he was always going to get the trip. It was a really good run and I’m thrilled with him.”