London’s police chief has warned there could be more units of would-be bombers planning attacks on the British capital. After police arrested nine people in Tooting in south London this morning, Met Commissioner Sir Ian Blair said London remains on high alert. “The second attacks on the 21st of July should not be taken as some indication of the weakening of the capability or the resolve of those responsible. This is not the B-team. These weren’t amateurs. They made a mistake. Just one mistake and we’re very, very lucky,” said Ian Blair. Residents in Tooting say police arrested three Turkish men who worked in and lived above a fast-food restaurant. The other six were arrested at a house nearby. The arrests bring to 20 the number of people in police custody, including one of the four men suspected of being behind last Thursday’s failed attack in London.