Dramatic new evidence linking Al Qaeda to the London attacks has emerged as a terrorist in US custody identified one of the bombers, police said today.The Al Qaeda aide, Mohammed Junaid Babar — who attended a ‘‘terror summit’’ in Waziristan, in tribal areas of Pakistan, last year — told investigators in USA that he recognised Mohammed Sidique Khan, the 30-year-old who triggered a bomb at Edgware Road station.Babar is reported to have picked out Khan after being shown photographs of the four suicide bombers who killed at least 55 people on July 7.Babar — an American national of Pakistani origin and a computer expert — was arrested on his return to the US from the Al-Qaeda summit in Waziristan.He has admitted a string of charges, including helping a foiled plot to bomb restaurants, pubs and railway stations in Britain, and has subsequently provided authorities with valuable information about the worldwide terrorist network.Khan, a teaching assistant from Dewsbury, West Yorkshire, is known to have had links with an individual who came to police attention during an anti-terrorist operation in March 2004.Germaine Lindsay, another of the London bombers, reportedly had links with terror suspects in New Jersey and was on the US ‘‘watchlist’’.British officers reached Cairo yesterday to interview Magdi El-Nashar, a biochemist enrolled in Leeds University, which was used as a bomb factory. -PTI