A teenage boy was being questioned yesterday on suspicion of attempted murder after a police officer was stabbed during an undercover operation in London.
The injured officer was knifed three times in the stomach and had major surgery after being taken to hospital on Tuesday night. His condition was yesterday described as serious but not life-threatening.
The plain-clothes officer, attached to a Specialist Crime and Operations Unit of the Met, was deployed on a pre-planned operation in Bow. He is thought to have been targeting a criminal gang when he was attacked by a group of teenagers in an alleyway next to the Bow Bells pub at 9.22pm.
Scotland Yard yesterday said the assailants included three boys and a girl in their late teens. It is not believed the group knew that the person they attacked was a police officer. They may have been out socialising in the area.
Police think the youths could have been involved in another attack nearby, outside Devons Road DLR station, where they threatened a motorist with a knife. He managed to drive off and reported the threat to police.
A pub worker told the Standard he saw four youths dive out of the alley and flee past him down the busy high street.
“Two young kids and one girl ran past, then a fourth guy came after them,” he said. “They were all very young, aged under 15, and they ran off towards McDonald’s. Then the police came past in – and I’m not exaggerating – no more than 10 seconds.”
Temporary deputy assistant commissioner Richard Martin, of specialist crime and operations, said: “Fortunately the officer is recovering well in hospital, as his injuries could have been a lot worse. I appeal for information or witnesses.”
Police said the covert operation was not terrorist-related. 
Surrounding streets were sealed off to pedestrians and traffic within minutes as officers with dogs hunted the suspects. A knife was recovered and a male in his teens arrested.
The injured officer, described as a “sturdy” middle-aged man with tattoos, was seen being wheeled into a waiting ambulance.
Onlooker Saleh Ahmed, 45, was on his way home when he saw the flashing lights of emergency services and a police helicopter overhead. “There was a massive manhunt,” he said. “I haven’t seen anything like it. Police, helicopters, dogs everything – it was chaos.”
Locals said the alleyway, which backs onto a street of gated executive apartments and a primary school, is a known drug-dealing hotspot that has been the subject of numerous complaints.
The knifing comes after it was revealed that two police officers were attacked by a mob of 30 schoolchildren in Lewisham this month. One officer had serious bruising after being beaten to the ground in the attack.