London: A summer trip to the UK as a teenager and visits to Shakespeare’s birthplace convinced Osama bin Laden that the west was “decadent”, the late leader of al-Qaida and architect of the 9/11 attacks wrote in his personal journal shortly before he was killed by US special forces in 2011.

The journal is among 470,000 documents collected from the house where Bin Laden died that were released by the CIA on Wednesday . The agency said it had released the treasure trove “in the interest of transparency and to enhance public understanding of al-Qaida and [bin Laden].”

Though there have been previouse reports that Bin Laden travelled to the west, this is the first confirmation.

An entry in the nondescript school notebook describes how Bin Laden first travelled to “the west” for an unspecified “treatment” when he was in “sixth grade” and 13 years old.

The following year the teenager, the wealthy son of a billionaire Saudi construction tycoon, spent 10 weeks in Britain “studying”.

Bin Laden gives no further details, but he has previously been reported to have taken an English language course at Oxford .

In the journal, Bin Laden briefly describes visiting the home of William Shakespeare in Stratford-upon-Avon but says he was “not impressed” by British society and culture during his time in the UK.

“I got the impression that they were a loose people, and my age didn’t allow me to form a complete picture of life there,” he wrote. “We went every Sunday to visit Shakespeare’s house. I was not impressed and I saw that they were a society different from ours and that they were a morally loose society.

The journal was bought in a well-known bookshop in Pakistan a few hours drive from the garrison town of Abbottabad, where Bin Laden spent five years with his family before his death.

The journal appears to be partially written by Bin Laden’s son, Khalid, who was also killed in the Navy Seal raid, and sometimes takes the form of a question and answer session between father and son.

The journal entries are at times apocalyptic, describing the two men’s dreams and visions, including a scenario in which Muslim countries unite after the revolutions and peace is established with the west - a prelude to the end times in some branches of Islamic theology.

At other times, Bin Laden appears more practical, discussing recommendations for Al Qaida’s messaging in the aftermath of the revolutions to better capitalise on rising Islamist sentiments and to take advantage of the wave of popular unrest.

Bin Laden’s mention of his feelings towards the west after his time in Britain will interest experts. Most accounts of his life say he was radicalised as a student and later when he became engaged as a volunteer organiser for Arab foreign fighters taking part in the war against the Soviets in Afghanistan from around 1981.

The US government has released hundreds of documents over recent years, though this is the largest such release.

Among the material released by the CIA was some which suggested Bin Laden’s time in the UK may have had a deeper influence than he may have admitted.

Loaded on one computer was video of the Rowan Atkinson comedy Mr Bean dubbed in Pashtu, the local language in western Pakistan and eastern Afghanistan, and episodes of the animated programme Wallace and Gromit.

There were also more than 30 videos on crocheting.