In the wake of the Parsons Green bomb, our Government struck the right balance between reassurance and vigilance

Theresa May is right to say she will redouble official efforts to fight extremism, yet Donald Trump chose to be at his offensive worst

No government can prevent every terrorist getting through. However, they can plan for what happens when an attack does occur, and the authorities are now well-rehearsed (REUTERS)

It could have been much, much worse. So far as can be judged, the improvised device that caused dozens of casualties on a rush-hour tube train at Parsons Green was faulty, probably in its detonation mechanism.

Had it exploded as intended there would certainly have been many more injuries and, indeed, fatalities.

In that respect – but not necessarily any other – it was uncomfortably reminiscent of the 7/7 and, more particularly, the failed 21/7 attacks on London in 2005. Again, it is early to draw many definitive conclusions, but this device in a shopping bag and builder’s bucket is obviously not properly manufactured munitions, but homemade and, according to the early testimony of experts, in some respects comparatively sophisticated. Still, very little is known for sure; more will become clear as the forensics teams get to work on the remains of the bomb.

No government can prevent every terrorist getting through. However, they can plan for what happens when an attack does occur, and the authorities are now well-rehearsed. Firefighters responded within minutes, as did the police, and the Chelsea and Westminster Hospital, which treated most of the victims, was also able to implement its major incident process. Cobra once again coordinated the various official bodies reacting to the attacks. Sadiq Khan, Mayor of London, the Metropolitan Police and the Prime Minister all struck the right balance between reassurance and vigilance. A higher-profile armed police presence will assist with that.

Wise not to repeat her “enough is enough” declaration, Theresa May is right to say she will redouble official efforts to fight extremism, wherever it comes from – and much of it is homegrown. In that respect the police are right to take action, in due course, against the racially motivated hate circulating on social media. Any backlash of hate crime has to be resisted and prosecuted. As we have seen so often before, the professionalism and bravery of the emergency services was peerless. We must assume that the Government’s decision, taken on advice from the security services, not to raise the terrorist threat level is correct.

Yet again, though, what was a day of concerted action and a mostly unified front against terror, Donald Trump chose to be at his offensive worst. He has done this before about a terror attack in London. Now, tweeting again with no great knowledge of the situation or background, he chose to patronise the British authorities and, potentially, confuse the search for those involved.

Plainly, the “special relationship” has entered an uneasy stage in its development. As with his other interventions over terror, North Korea and the unrest in the southern United States, President Trump has a remarkable knack for creating division among those who should be natural allies. Theresa May was right to rebuke him. Whether he had been briefed or not before sending his tasteless tweet, he can only have had the patchiest of information; in any circumstance, his intervention was gratuitous and insulting.

Without desecrating such an event with politics, this is also a moment to consider once again the resources that the Government devotes to the police, security services and civilian departments in central and local government. They need the funds and the personnel to conduct surveillance, to run Prevent strategies, to respond to emergencies, to have a sufficiently high profile to deter and reassure, and to treat and operate on victims of terror. There is no getting away from that.

Government sources often tell us that many terrorist attacks have been prevented by effective intelligence work, and there is no reason to suppose that the numbers and determination of those intent on terror and murder are likely to subside in the near future. Quite the opposite, if this is affiliated to Islamist extremism, given the retreat of Isis in its so-called caliphate. The resources have to be found to fight this shifting pattern of terror.

For some time to come, the West will have to become accustomed to a continuing level of low- to medium-tech terror. Apart from trying everything to minimise the threat, the most important thing is to stop any spiralling of revenge or retaliation attacks and further division. That, even more than loss of life, is what these terrorists aim to achieve.