Low-level plots like Parsons Green need even more vigilance

London has now faced its fourth terrorist attack this year. As details emerge, new peculiarities are uncovered. The brutal reality, though, is that low-level terror plots like that at Parsons Green are becoming the norm.

This is not a tacit admission of defeat, but rather a warning that we are facing an increasingly diffuse threat. This means we all have to be alert, while the authorities need to maintain and even step up the tempo of their effort to stay ahead of the threat.

There are some novel peculiarities around the Parsons Green attack. A bomb left on an Underground train with a timer is something that had not been seen for some time. Most recent bombers seemed to have had suicidal intent.

While most recent plots have been conducted by UK-born individuals, the potential presence of refugees in this attack is not entirely new. IS’s pro-forma claim to be behind the attack lacks evidence of prior knowledge, but it is perfectly possible those responsible may have assimilated some of its ideology.

This is the larger context that the authorities are contending with: a threat made up of disparate individuals launching attacks using rudimentary and home-made means. The time it takes for them to be galvanised into action continues to shrink, and terrorist groups are emitting an ever more basic message to encourage sympathisers to launch attacks.

Given the easy access and diffuse nature of the ideology and attack methods it becomes very difficult to maintain complete cover. On top of this, the authorities are seeing more individuals who were previously under suspicion moving back into current investigations, and a continuing inflow of people from troubled areas — a limited number of whom may arrive with lethal intent.

The good news is that all terrorists are finding it increasingly difficult to launch large-scale coordinated plots.

The greater danger appears to be among the broader community from whom terrorists come. More work needs to be done tying together the many different information streams that authorities have access to and more thought given to how to prioritise them. And the pressure needs to be kept up in keeping known figures under adequate surveillance.

But there is a role for the public too. There is an onus on us Londoners to keep our eyes open.

As a child in London, I recall constant public campaigns about potential IRA devices on public transport. Tubes were held up by abandoned bags, but many attacks were prevented. There needs to be a return to this approach. We all need to keep our eyes open to protect the society in which we live.

Raffaello Pantucci is director of international security studies at the Royal United Services Institute (RUSI)