A spokesman for the Metropolitan Police said:
"All lines of inquiry were considered in the early stages of the investigation. The investigation was detailed and complex and officers had a duty to explore every avenue of inquiry and retain an open mind about the circumstances.
"They carried out numerous actions including door-to-door inquiries, leaflet drops, searches, interviews and forensic analyses.
"The CCTV evidence took some time to collate and analyse but then clearly showed a veiled suspect trailing the victim before the attack.
"Konye was arrested as the investigation progressed."
More top news
Hundreds of passengers were ordered to leave the terminal building and flights grounded after passengers suffered difficulties breathing.
Council leaders today called on the government to provide extra money to help resettle the youngsters in the capital.
An eyewitness said: "It was very unnerving. It was just after 12pm and there were suddenly police vans and cars everywhere."