British police have arrested an 18-year old woman at a London airport on suspicion of preparing acts of terrorism and membership of a banned organization, a police statement said. Her arrest on Friday after she arrived on a flight at Stansted airport was connected to a prior investigation which had already resulted in the arrest of a 21-year-old man in October last year. The arrest is the latest in a ****** carried out by British counter-terrorism ******rs since the country's threat level was raised in August to its second-highest level because of risks posed by Islamic State fighters returning from Iraq and Syria. British Prime Minister David Cameron is in the United States for two days of talks with President Barack Obama where they have said they would tackle the threat posed by extremists.