Tominator got up in the dying strides to reclaim his crown in a pulsating John Smith's Northumberland Plate.
The grey was a 25-1 winner of the Pitmen's Derby in 2011 when trained by Reg Hollinshead, but now with Jonjo O'Neill having initially been bought to go jumping, the six-year-old was a strongly fancied 8-1 shot, despite carrying the burden of top-weight.
Given a typically patient ride by Lee, the gelding gradually made ground through the field, but still looked to have plenty of work to do heading inside the last furlong of a two-mile journey.
Oriental Fox looked likely to prevail when coming down the outside of the field, but Tominator really got going as the post loomed and he got up to take the prestigious prize by a short-head.
Lee, completing a big-race double after his Chipchase success, said: "Happy days are here again! Massive credit to the horse and massive credit to Jonjo. He told me to be brave on him. The horse gave me a great ride."
O'Neill said: "Graham is a brilliant jockey and a great tactician. He knew everything that was happening and did everything right. He's a very good rider and the horse produced on the day.
"I thought he had plenty of weight, but it came right. It's brilliant."
On becoming the first dual Northumberland Plate winner since Tug Of War secured back-to-back successes in 1977 and 1978, the trainer said: "It's fantastic. It's great to be part of it all. I'd love to have more Flat horses. We'll get a few more now, hopefully."