Defoe (11-4 favourite) followed up his Group One win at Epsom to land the Hardwicke Stakes on the final day of Royal Ascot 2019.
Roger Varian's five-year-old won for the first time at the top level when holding off Kew Gardens in the Coronation Cup at the end of last month. And, under Andrea Atzeni, he continued in sparkling form to run out a fine winner of the Group Two contest on day five of the Royal meeting.
He now looks set to return to Ascot next month in a bid for more Group One success in the King George VI And Queen Elizabeth Stakes in what could be the race of the season.
Defoe is now as low as 5-1 for the midsummer middle distance championship contest behind Prix de l'Arc de Triomphe heroine Enable, who is the general 5-2 favourite.
The son of Dalakhani - who is a best-priced with Paddy Power, bet365 and Skybet - could also take on fellow Royal Ascot winners Crystal Ocean and Japan; while recent Investec Derby hero Anthony Van Dyck and last year's Arc runner-up Sea Of Class could also pitch up back at the Berkshire track for what could be a mouthwatering contest.
Defoe, though, at least booked his spot in the line-up with his latest success.
Having been held up in rear off the pace set by Salouen, Defoe came through on the turn for home, swooping down the outside to take the lead.
But he had to dig deep as 25-1 outsider Nagano Gold came flying behind him, under Christophe Soumillon. Defoe held on by half-a-length, with the Sir Michael Stoute-trained Mirage Dancer (6-1) a further length away in third.
The runner-up was involved in an incident at the start when last year's returning Derby hero Masar stumbled badly, nearly unseating jockey James Doyle with, Nagano Gold caught behind with nowhere to go.
For Defoe, everything went smoothly and winning jockey Atzeni said: "It's great. It's a tough week and hard to get winners. He's very straightforward.
"It's great for the owner as he's here today and has been here all week."
Trainer Varian pinpointed the King George as the likely next target.
The Newmarket trainer said: "I thought it was a strong race on paper, and he took his form from Epsom forward, which was nice.
"I'm grateful to Sheikh Obaid and delighted for him that he has got on the scoresheet, and I'm delighted for Andrea, too.
"He is just a lovely horse. He is very straightforward, tries and relaxes and is getting better with age. He is a joy to train. I thought he was very capable of mixing it with the best and the horse is warming to the season nicely.
"Hopefully we can bring him back in one piece for the King George. It is up to other people to have their opinion, but I have my opinion of the horse which is very high, and he is backing that up with his performances.
"We are excited for the rest of the season."
On the Godolphin-owned Masar, who finished fifth on his first start since winning last year's Derby, jockey Doyle said: "He tripped over coming out of the gates, which is obviously not ideal in a race like this, but that's horse racing. It's annoying, but we'll move on."
