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This Week: Roisín Duffy examines the global threat of terrorism and the measures taken by countries around the world
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This Week: John O'Connor, New Scotland Yard, discusses the intelligence gathering methods of the British security forces
Anti-terrorist police in London have been given more time to question a man arrested in connection with last week's bombings in which 55 people are known to have died.
Scotland Yard has identified the fourth suspected suicide bomber as 19-year-old Germaine Lynsey who was born in Jamaica and carried out the Kings Cross attack.
Police have released CCTV footage of all four men whom they believe carried out the attacks.
The men were recorded together at Luton station in the north of the city just hours before the four explosions.
