Two men are being questioned about the explosion on a London Underground train on Friday, September 15. Sputnik spoke to a terrorism expert who said there was little that could be done to protect passengers in Europe.
Dr. David Lowe, a former police officer turned security consultant, said the incident at Parsons Green in west London was clearly caused by a "crude device."
"It seemed to have been made by someone who was really not trained in explosives. My first concern was that people were very, very lucky. If that had gone off properly we would have been looking at fatalities," Dr. Lowe told Sputnik.Dr. Lowe said this was the first attack on London's Tube network since 2005, when three suicide bombers blew themselves up.
A second attack, on July 21, 2005, failed when the devices, hidden inside rucksacks, of four more suicide bombers failed to go off.
But Friday's attack came only months after a suicide bomb attack in Manchester and incidents involving vans, cars and knives in Westminster and Borough Market in London.
"We have to ask now 'is this the new norm?' " said Dr. Lowe, who drew comparisons with the Irish Republican Army's campaign of terror, which lasted throughout the 1970s and 1980s and well into the 1990s.
"The Provisional IRA's England department generally phoned in a coded warning but these people give no warning at all. In fact they are prepared to kill themselves. It is a very sad state of affairs," he told Sputnik.
He said Daesh were very quick to claim responsibility for the Parsons Green attack, but there was no evidence they actually had any knowledge of it beforehand, let alone plotted it.
"We have to be pragmatic. With the sheer volume of passengers on the underground network, not just in London but across major European cities, there is no way of preventing this but what we have got to do is be a bit more vigilant. If you see a suspect package and someone has left it, pull the emergency cord and try to evacuate the scene as soon as possible," Dr. Lowe told Sputnik.
But he admitted it was very difficult, especially if someone leaves a train at one station and sets the timer to go off before the next stop.
He said Tube passengers were accustomed to using the network without airport-style checks and it would be impractical to introduce such screening.
An 18-year-old man, who was arrested at Dover in Kent over the weekend, and a 21-year-old man, who was arrested in Hounslow, west London, are both being questioned by police over Friday's incident, which injured 30 people.
The device partially detonated at 8.20am as hundreds of commuters were traveling into work in central London.
CCTV footage has now emerged of a man carrying a plastic supermarket bag 90 minutes before the incident.
Police are searching addresses on the south western outskirts of London.
Home Secretary Amber Rudd said police had made "good progress" in the investigation and urged "everybody to continue to be vigilant but not alarmed."