"A British al-Qaida sympathiser living in Derby volunteered last year to help with a terrorist attack on targets in Denmark including the offices of the newspaper that published cartoons of the prophet Muhammad, secret documents obtained by the Guardian reveal. A second British man is alleged to have handed over cash for the plot.

The two men were visited in August 2009 by David Headley, an extremist born in Pakistan but raised in the US, where he is now in custody. Headley, who was arrested two months later, was working for Ilyas Kashmiri, a senior Pakistani militant with links to al-Qaida.

Kashmiri, whom al-Qaida leadership figures have named as part of Osama bin Laden's group, told Headley to focus on a plan to attack the offices of the Danish Jyllands-Posten newspaper, which had published controversial cartoons of the prophet in 2005. He gave Headley $1500 (£954) to finance a surveillance trip. More general attacks in Denmark were also discussed. Headley said he understood that they might involve suicide bombings.

According to the documents, Kashmiri told Headley the two men in Derby – who were originally from Kotli, in north-east Pakistan – would help him. It transpired that one of the men had fallen out with Kashmiri, accusing the militant leader of allowing his son to steal funds for jihad, but he did agree to provide money for the mission; the other man "was available" for the attacks in Denmark, the documents reveal. These are based on 34 hours of interviews with Headley conducted by Indian investigators this summer.

They also describe in detail how Headley, having been deeply involved with the Lashkar-e-Taiba group in Pakistan and having conducted repeated surveillance trips for the Mumbai attacks, became involved with Kashmiri and, at one remove, al-Qaida. After spending six years with Lashkar, Headley said he became "mentally distanced" from the group and felt that the global agenda of Kashmiri and al-Qaida suited him better."

Image by keerthi via Flickr

The plea agreement discloses details of Headley's planning and trips he undertook to plan the Mumbai attacks. He admitted that he had attended training camps in Pakistan operated by the Lashkar-e-Taiba, a designated terrorist organisation, on five occasions between 2002 and 2005. In late 2005, he received instructions from three Lashkar members to travel to India to conduct surveillance, which he did five times, leading up to the attacks three years later.

A written plea agreement containing a detailed recitation of Headley's participation in the foreign terrorism conspiracies was presented to the court, when he changed his plea to guilty, says the Federal Bureau of Investigation (FBI). Headley has cooperated with the government since he was arrested on October 3, 2009, and the plea agreement states he “has provided substantial assistance to the criminal investigation,” and also “information of significant intelligence value.”

In light of Headley's past cooperation and expected cooperation in future, the prosecutors will not seek the death penalty for him. When directed by the U.S. Attorney's office, he must “fully and truthfully participate in any debriefings for the purpose of gathering intelligence or national security information, and Headley further agrees that, when directed by the United States Attorney's Office, he will fully and truthfully testify in any foreign judicial proceedings held in the U.S. by way of deposition, videoconferencing or letters rogatory.”

As for sentencing, which will be deferred until after the conclusion of Headley's cooperation, the plea agreement calculates an anticipated advisory sentencing guideline of life in prison. If Headley continues to provide full and truthful cooperation, the government will ask the court to grant an unspecified departure from the sentencing guidelines. This is solely up to the court to decide.

Headley pleaded guilty to conspiracy to bomb public places in India; conspiracy to murder and maim persons in India; six counts of aiding and abetting in the murder of U.S. citizens in India; conspiracy to provide material support to terrorism in India; conspiracy to murder and maim persons in Denmark; conspiracy to provide material support to terrorism in Denmark; and conspiracy to provide material support to the Lashkar.

According to the plea agreement, Headley attended training camps operated by the Lashkar: a three-week course, begun in February 2002, that provided indoctrination on the merits of waging a jihad; a three-week course, which started in August 2002, for training in the use of weapons and grenades; a three-month course, starting in April 2003, that taught close combat tactics, use of weapons and grenades, and survival skills; a three-week course, begun in August 2003, that taught counter-surveillance skills; and a three-month course, begun in December 2003, which provided combat and tactical training.

After receiving instructions from three Lashkar members in late 2005 to travel to India to conduct surveillance, Headley in February 2006 changed his name in Philadelphia from Daood Gilani to facilitate his activities on behalf of the Lashkar by portraying himself in India as an American who was neither Muslim nor Pakistani. In the early summer of 2006, Headley and two Lashkar members discussed opening an immigration office in Mumbai as a cover for his surveillance activities.

Headley eventually made five extended trips to Mumbai — in September 2006, February and September 2007, and April and July 2008 — each time making videotapes of various potential targets, including those attacked in November 2008. Before each trip, Lashkar members and associates allegedly instructed Headley on specific locations where he was to conduct surveillance, and after each trip he travelled to Pakistan to meet Lashkar members and associates, report on the results of his surveillance and hand over surveillance videos.

Before the April 2008 surveillance trip, Headley met co-conspirators in Pakistan and discussed potential landing sites in Mumbai for a team of attackers who would arrive by sea. He returned to Mumbai with a Global Positioning System device and took boat trips around the Mumbai harbour and entered various locations into the device, according to the plea agreement.

Starting November 26 and continuing through November 28, 2008, ten attackers, trained by the Lashkar, carried out multiple assaults with firearms, grenades and improvised explosive devices against multiple targets including the Taj Mahal and the Oberoi hotels, Leopold Café, the Chabad House and the Chhattrapati Shivaji Terminus, each of which Headley had scouted in advance.

In March 2009, Headley made a sixth trip to India to conduct additional surveillance of, among others, the National Defence College in Delhi, and the Chabad Houses in several cities.

As for the Denmark plot, Headley admitted that in early November 2008, he met a Lashkar member in Karachi and was instructed to conduct surveillance of the Copenhagen and Aarhus offices of Morgenavisen Jyllands-Posten, in preparation for an attack in retaliation for the Danish newspaper's publication of cartoons on Prophet Muhammad.

In late July and early August 2009, Headley travelled from Chicago to various places in Europe and met and attempted to obtain assistance from the al Qaeda leader, Ilyas Kashmiri's contacts and, while in Copenhagen, he made 13 additional surveillance videos. When he returned to the U.S. on August 5, 2009, Headley falsely told a U.S. Customs and Border Protection inspector in Atlanta that he had visited Europe for business reasons.

After returning to Chicago, Headley spoke with Abdur Rehman, a co-defendant, on the phone and, using a code, described his surveillance activities and his meeting with Kashmiri's European contact. On multiple occasions in mid-2009, Headley communicated with Abdur Rehman about planning the attack and media reports that Kashmiri had been killed. On October 3, 2009, he was arrested at the O'Hare International Airport in Chicago. He was intending ultimately to travel to Pakistan to deliver the 13 surveillance videos to Abdur Rehman and Kashmiri, the plea agreement states.

One of Headley's co-defendants, Tahawwur Rana, 49, of Chicago, who was indicted in January on three counts — conspiracy to provide material support for the Mumbai attacks; conspiracy to provide material support for the Denmark plot; and providing material support to the Lashkar — has pleaded not guilty and remains in federal custody in Chicago, awaiting trial. Abdur Rehman and Kashmiri, who were charged in the same indictment with conspiracy to murder and maim persons in Denmark and providing material support for the Denmark plot, are not in U.S. custody.