The Met said that the force does not have specific information relating to the location or timing of the bomb, but shut off areas surrounding Buckingham Palace and Trafalgar Square following a coded warning.
During “the Troubles” — the often violent campaign by Irish republican groups calling for the reunification of the divided Ireland — terrorists routinely telephoned media outlets ahead of attacks using messages with specific codes that allowed police to distinguish them from hoax calls.
The bomb threat underlines the renewed threat posed by Irish republican dissident groups to the United Kingdom. Officially the Irish Republican Army and its principal successor groups have disarmed and joined the peace process but a recent resurgence in threatening rhetoric in Northern Ireland culminated in the murder of a Catholic police officer, Ronan Kerr, in Omagh in April.
The UK government upgraded its threat level from Irish dissidents from “moderate” to “substantial” in September 2010.
Dissident groups have said that the Queen would be a legitimate target during her visit. Security consultancy Exclusive Analysis wrote in a note to clients that there was a high risk of attacks on British security forces and police personnel in Northern Ireland, and of hoax attacks in the Republic, during the sovereign’s visit.
David Lea, an analyst at Control Risks, told CNBC.com that Monday’s threat was most likely intended to be “symbolic”.
“A lot of the reaction on Monday was about ‘is this a return to the 1980s and 1990s?’ and that effectively is what it was designed to engender, rather than to cause an explosion,” he said.
“There is a capability [within the dissident groups] but I’m not sure there’s an intent to attack the UK. I don’t think they are particularly keen on triggering a massive clampdown on both sides of the Irish border, which there certainly would be were there to be anything more than a small, symbolic and non-threatening attack,” Lea explained.
The current dissident groups are believed to be based around a core from the IRA’s split in 1997, and while they have demonstrated their capacity for striking in Northern Ireland, their ability to perform similar attacks in London is in doubt.
“There is a very big distinction between attacking in Northern Ireland and attacking in London. I don’t think that’s a line that anyone is willing or capable to cross,” Lea said.
While it would be dangerous to dismiss any threat where the proponents have demonstrated an access to weaponry, it is highly unlikely that anything of the scale of the 1993 Bishopsgate truck bombing in London’s financial district is within their current capacity, Lea said.
“If that were to happen it would be a long way away, and we’d see all sorts of intermediate stages, smaller attacks… The dissident republican’s MO in London was small attacks in suburbia, Hammersmith, the Hendon post office, that kind of thing, rather than spectacular attacks on Central London,” he added.