The eccentric Hollywood star, who was the bookies’ favourite to win the show, beat Olympic boxing champion Audley Harrison to the title after receiving the most votes from the public.
As he emerged from the Big Brother house to cheers from the crowd, Gary told host Emma Willis: “I know why the word ‘Great’ is in front of ‘Britain’.”
Gary, who is the first American to win the UK version of the show, added: “It’s a feeling of surprise and honour and a tribute to my love for this country.”
The Lethal Weapon star and former Oscar nominee, who clashed with a number of his famous housemates, said he had no idea what to expect from the show.
“When you’ve been around the sun 70 times – that’s how old I am – you’ve got a new knowledge of life and a new knowledge of humour, you learn to respect the youth,” Gary said. “When I get back home I’m a changed man.
“I didn’t think I was selfish. I didn’t think I was lazy. I didn’t think I was insecure. This show showed me things about myself that you need to change brother.”