Philip Ingram, a former senior intelligence and security officer, said despite the crude nature of the devices, the seriousness of the matter should not be underestimated.
He said: “While this was not the most sophisticated device, someone had put together a viable incendiary device that has managed to remain viable through the international post and then ignite when it was opened, which is exactly what it was designed to do.”
Deputy Assistant Commissioner Dean Haydon, the senior national coordinator for counter-terrorism policing, said there was still no clear motivation behind the incidents.
He said: “We are talking to our Irish counterparts but at the moment there’s nothing to indicate motivation of the sender or ideology, so I cannot confirm at the moment if it’s connected to any Ireland-related terrorist groups.”
Police have also warned there could be more parcels and urged vigilance for those handling mail.
Commander Clarke Jarrett, head of the Met’s Police Counter Terrorism Command, said: “We have issued extensive advice to transport hubs and mail sorting companies to be vigilant for and report suspicious packages to police, as always we encourage anyone who sees something suspicious to report it.”