The security services are checking possible links to Ansar al-Islam, a radical Kurdish terrorist group sponsored by al Qaeda, in the widening inquiry into the Glasgow and London bombs.

The Herald understands that MI6 warned the British government last April that Ansar might stage attacks in the UK to coincide with the end of Tony Blair's premiership. Mullah Krekar, its leader - now under arrest in Norway - announced that "many martyrs are ready to blow themselves up" and added that Britain should expect an attack in retaliation for its continuing military involvement in the Middle East.

Ansar's speciality is suicide attacks and car bombs. Its agents killed 109 Kurds in a double suicide strike against the two main local political parties' offices in Irbil in 2004.

It also claimed responsibility for shooting down a Kinloss-based RAF Hercules transport aircraft north of Baghdad in January, 2005, killing all nine aircrew and an SAS soldier in the largest single loss of life sustained by Britain in Iraq in the past four years.

The group, which also includes Arabs and Iranian-born Kurds, follows the Taliban line of believing in strict sharia law.

Its fighters, who call themselves the Ansar al-Sunnah Army, videotaped the execution of 22 Nepalese construction workers in August, 2004. The men were shot or beheaded and footage of the atrocity posted on the internet.

Dozens of Ansar's estimated 1000 members have been caught in a string of arrests across Europe in the past two years. The organisation is known to have cells in Britain, Germany, Italy, Spain, Turkey and Sweden.

Formed in 2001 in north-eastern Iraq, it received cash and military training support from al Qaeda.

The terror network then called in the favour by using Ansar's enclave on the Iranian border as a safe haven for its jihadis fleeing the US-led invasion of Afghanistan.

The group's last known leader is a Kurd - Warba Holiri al-Kurdi - who now goes by the name of Abu Abdallah al-Shafi.

Iran's Shia regime is understood to have offered refuge to Sunni Ansar because the terror group shares its opposition to a Kurdish homeland ruled by anti-Iranian political parties.

However, although the attacks in Glasgow and London bore the hallmarks of an al Qaeda plot, analysts say they lacked one key ingredient: professional execution.

While details are still emerging about the men and the methods behind the attempts, analysts say the apparent slipshod planning indicates the group may have been amateurs working without the guidance or direct support of masterminds in Pakistan or the Middle East.

None of the makeshift bombs managed to detonate, and the only serious injury was sustained by one of the alleged perpetrators, who set himself ablaze.

But for all the failures, the attacks did accomplish a key goal: creating fear and havoc throughout Britain as police cordoned off streets to search 19 buildings, stepped up stop-and-search procedures and banned cars from approaching terminals at many airports.

"Even bombs that don't go off have worldwide repercussions, and I think this is part of the terrorist calculus as well," said terrorism expert Bruce Hoffman