Updated May 25, 2017 09:48:39

Photo: The ability to swoop on those who may think they are safe from detection can be a decisive advantage. (Reuters: Neil Hall)

If only the Manchester bomber had acted alone.

His power to kill and maim is thankfully over. But now it's clear he was part of a network and it's possible the bomb maker is still free to ply his ghastly trade once again.

Authorities can't ignore the possibility the Manchester bomber was part of a wider cell in Britain, writes James Glenday.

Finding young, impressionable people willing to kill themselves in order to murder others is not the hard part. There are recruiters skilled at grooming suicide bombers.

But getting bomb-makers that can build and deploy their devises in Western countries is far more difficult.

The conflicts in places like Syria and Libya have vastly increased the number of fighters who are now well educated in various means of murder.

And some of them are returning home to countries like Britain.

With the arrests in the UK and now Salman Abedi's brother and father's in Libya, authorities will be hoping they have shut down any terror cell.

But it's far from clear how wide the network is spread or if those arrested are indeed part of it.

One weapon the security agencies jealously guard is the power of surprise.

The ability to swoop on those who may think they are safe from detection can be a decisive advantage. Sometimes it is the information withheld that proves so effective.

So, you can imagine the anger from authorities when The New York Times published official crime scene photos and details. They included images of what looks like the detonator, shrapnel and fragments of a backpack.

The colours match CCTV footage released separately that appears to show Abedi carrying the distinctively coloured backpack.

What will no doubt worry investigators is the apparent sophistication of the improvised device.

It's possible but unlikely the suicide bomber built the bomb himself. If not, then more attacks are quite possible.

That might be why the terror warning was raised to the highest level and the reason thousands of armed soldiers would now be guarding important buildings like the parliament and the Prime Minister's residence.

Photo: Members of the army have been deployed to guard "key locations" including 10 Downing Street. (AP: Lauren Hurley)

It's now clear Abedi was already on the radar of security services. Hard questions will no doubt be asked about how they missed this deadly attack.

The answer may simply be he wasn't high on the risk list. It's simply impossible to track every suspect 24 hours a day.

Here is what we know so far about the man suspected of killing 22 people with a nail bomb in Manchester at an Ariana Grande concert.

And the British intelligence agencies have a strong record at preventing horrors like this. But not this time.

Despite the official warnings and the residual fear after the Manchester outrage, the tourists were still taking their selfies and craning their necks to see Big Ben. Maybe some stayed away, but the pavements around Parliament appeared as busy as ever.

All the tourists I spoke to said they were reassured, not worried, by the sight of armed soldiers around public buildings.

A young Frenchman said the attack reminded him of what has happened in his country in the last couple of years.

"It's life," he told me. Unfortunately, for the moment, he's right.

Topics: terrorism, unrest-conflict-and-war, law-crime-and-justice, crime, united-kingdom

First posted May 25, 2017 08:22:32