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Video - DeGale wins opening fight
British middleweight boxer James DeGale got his Olympic campaign off to a flying start with an impressive 13-4 victory over Egypt's Mohamed Hikal.
Trailing 3-2 after the first round, the London southpaw fought back in style.
DeGale, 22, will now face American Shawn Estrada who comfortably beat Ezequiel Osvaldo Maderna 10-2.
The victor is likely to come up against reigning world champion Mayvey Korobov in a daunting quarter-final after the Russian beat Naim Terbunja 18-6.
Korobov is regarded as one of the most talented boxers at the Olympics and lived up to the billing by easily outpointing his Swedish opponent in the tournament's opening bout.
The 25-year-old won the world amateur title at Mianyang 2005 and then Chicago 2007 and, with Athens gold medalist Gaydarbek Gaydarbekov now out of competition, Korobov is the firm favourite for gold.
We were all a bit down after what happened to Frankie then getting a bad draw but I've got the team off to a good start and the team should be buzzing now
DeGale's triumph, meanwhile, will help lift the gloom over Britain's boxing team after the disappointment of Frankie Gavin's late withdrawal from the Games.
The 2006 Commonwealth Games bronze medallist made a tentative start in the first round but in the second he scored three unanswered points for a 5-3 lead.
Hikal, a former world amateur bronze medallist, won just one point in the last three rounds as DeGale found his best in the final minutes, firing single shots with unerring accuracy and totally dominating the experienced 29-year-old.
"I was fighting a good fighter and in the last two rounds I got my rhythm but I still wasn't at my best," said DeGale.
"This is the biggest show on earth and I was a bit nervous. That pressure will be off me a bit in the second round.
"We were all a bit down after what happened to Frankie then getting a bad draw. But I've got the team off to a good start and the team should be buzzing now."
British light-heavyweight Tony Jeffries received a first round bye but his potential rival, the experienced Irishman Kenny Egan, got his campaign started with a 22-2 win over Julius Jackson of the Virgin Islands.
"There's a long way to go but as long as I stay clear of injuries I like my chances in this tournament" said Egan. "I won't be satisfied unless I go home with gold."
Russian light-heavyweight Artur Beterbiev, wrapped up the afternoon session with a 15-3 win over Kennedy Katende.
But the large crowd at Workers' Gymnasium was most interested in China's light-heavyweight Zhang Xiaoping.
Zhang laboured to a 3-1 victory over Tunisia's Mourad Sahraoui, scoring two points in the final round of a disappointing bout.
Ghana's Bastie Samir scored the tournament's first legitimate knockdown in the first round of his light-heavyweight bout, flooring Nigeria's Dauda Izobo with a left hand.
Samir again knocked down Izobo in the second round to seal victory.
Samoan light-heavyweight Farani Tavui was taken to hospital on Saturday for "routine" tests after he was knocked unconscious by his Croatian opponent Marijo Sivolija-Jelica.
Charles Butler, head of the International Amateur Boxing Association's medical commission, said the 22-year-old was unconscious "for a very short period".
"I feel very confident that this young man will be okay," said Bulter of Samoa's solitary boxer in Beijing.
On Sunday light-welterweight Bradley Saunders opens against Ghana's Samuel Kotey while welterweight Billy Joe Saunders starts against Turkey's world number three Adem Kilicci.