When David Cameron addressed an emergency session of parliament convened in the aftermath of four consecutive nights of rioting and looting across England, he quickly turned to the supposed role played by social media.
"Everyone watching these horrific actions will be struck by how they were organised via social media," the prime minister told the House. "We are working with the police, the intelligence services and industry to look at whether it would be right to stop people communicating via these websites and services when we know they are plotting violence, disorder and criminality."
His claims were backed by some MPs and senior police, who revealed they had considered switching off social network sites at the height of the disturbances, but were unsure of their legal powers.
Yet preliminary analysis of how Twitter was used during the unrest presents a more complex picture, showing little immediate evidence that the social network was used to orchestrate disorder.
The Guardian has compiled a unique database of more than 2.5m tweets containing keywords, phrases and hashtags linked to England's riots.
Preliminary analysis of this Twitter activity in 12 riot locations shows the majority of surging social media traffic occurs after the first verified reports of incidents in an area, which could suggest that Twitter was used far more by those seeking to follow fast-moving events than to incite trouble – although it is not possible to say it played no role.
The tweets also reflect a shift in social media use during the week. Most reports place the initial disturbances in Tottenham between 8pm and 9pm on Saturday night. The number of tweets referencing the area surged in the wake of these first troubles: up from 15 between 7pm and 8pm to 15,000 between 10pm and 11pm.
Later in the week Twitter may even have helped spread warnings about trouble. On the following Tuesday Greater Manchester police gave a press conference at 2pm warning of potential issues later that day. This was mirrored by tweets mentioning the city jumping to over 1,000 an hour before trouble began, peaking at around 12,000 an hour after disturbances had started.
In areas such as Hackney Twitter filled with reports of stores closing early and police presence building in the area, hours ahead of the outbreak of trouble.
The Guardian database, which contains riot-related tweets sent between midnight on 6 August – the day riots began in Tottenham – and 8pm on 17 August, will be subject to more advanced analysis in the coming weeks as part of an ongoing investigation into the riots.
Several Facebook users have already been imprisoned for their use of the service during the unrest.
Two men who attempted to use Facebook to arrange riots, which did not materialise, were sentenced to four years in prison, while David Glyn Jones, 21, who posted: "Given the chance I'd love to smash up a police car, wouldn't you?", was sentenced to four months. The prime minister said he supported the "tough message" the court rulings had sent out.
Anecdotal evidence suggests BlackBerry Messenger was also used by some rioters to disseminate messages inciting unrest. However, the free pin-protected service, popular among young people, was also used extensively by those seeking to avoid trouble.
Executives from Facebook, Twitter and the BlackBerry manufacturer RIM, who have been resisting calls to shut down their networks, are to meet the home secretary to discuss further action.
