The 58-year-old's "unbridled happiness" was clear as he tied the knot with corporate lawyer Graham Cooper.
Paul – famously described by Diana as "my rock"— wore a kilt and full highland dress as he donned a red tartan that he had personally designed.
Speaking after the ceremony, a tearful Paul said: "Everything about the day has been perfect, made even more wonderful by the fact that my two sons were here to share in the occasion."
"There's no more hiding my unbridled happiness now. Life is about being true to who you are and, for the first time ever, I'm able to stand proudly beside my husband and say 'This is who I am'," he added.
The couple made headlines around the world last month when Paul came out as gay. The pair – who met on a train ten years ago — exchanged vows at a luxury five-star hotel in the Lake District surrounded by 60 close friends and family.
Guests cheered as the two grooms were legally married in a poignant 30-minute ceremony at a hotel overlooking picturesque Lake Windermere.
Paul's two sons, Alex, 32, and Nick, 28, flew in from America to see their dad marry his long time boyfriend . Ex-wife Maria, who Paul divorced last year following a lengthy separation, remained at her home in Orlando, Florida.
Paul's highland attire was a personally designed red, Macmillan-based tartan recognized by The Tartan Society. Its red stripes were in tribute to his service to Diana, the gold thread was a nod to his years of service to the Queen, and the jungle green stripe was an acknowledgement to his appearance on ITV's I'm A Celebrity, Get Me Outta Here.
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