Counter-terrorism expert Richard Barrett has raised the possibility that the Woolwich attackers may have been "copycats" of the Boston bombers.
I don't think we have seen much of this in terms of attacks on armed service personnel in the UK before.
It may be that this is a copycat after the Boston bombings. That two individuals could cause a lot of mayhem is maybe more of an inspiration than attacking soldiers.
The former United Nations co-ordinator for the al Qaida and Taliban monitoring team, who has served with MI5 and MI6, said it was clear the attackers wanted to "explain" their actions:
It looks like an attack which has certainly been done for effect. The way that they are hanging about and wanting to be arrested and explain what they were doing fits a pattern of people who want to send a message.
ITV News has uncovered a video showing Woolwich suspect Michael Adebolajo speaking at a demonstration at Harrow Central Mosque in 2009.
Documents suggest Security Services were trying to recruit Woolwich suspect Michael Adebolajo and had also approached members of his family.
Police in Kenya say they did everything they could to highlight their concerns about Michael Adebolajo.