<< The Karmapa The 17th Karmapa prior to his first press conference in 2001. Photograph: Arko Datta/EPA

The Karmapa had unwittingly become a key player in the complicated political game of Tibetan Buddhism under the Chinese in 1992 when at eight years old he became the first reincarnation to be recognised by both the Dalai Lama and the Chinese government.

He has now been living in extreme confinement for over 10 years. Only once was he allowed to leave India, in 2008 when permission was finally given for him to visit the US. Time, Newsweek and the New York Times, all carried major stories, hailing him as a significant future leader.

Why is this happening?

The Karmapas predate the Dalai Lamas by over 400 years. Unlike the Dalai Lama's dual role of spiritual leader and de facto king, the Karmapas have always been purely religious teachers revered for their enlightened powers. But the escape from Tibet on the eve of the new millennium into the welcoming arms of the Dalai Lama immediately made the 17th Karmapa into a poster boy for the Tibet cause.

The Karmapa's intention had been to receive the oral instructions of his lineage from his spiritual masters in India and to reclaim his monastic seat in Sikkim where his predecessor had settled in 1959 on his escape from Tibet. But on arriving in India he found himself banned from both his teacher's monastery near Dharamsala and Sikkim. The Dalai Lama promptly housed him in temporary quarters in two rooms at the top of Gyuto monastery. The Dalai Lama and the Karmapa belong to different schools of Tibetan Buddhism. It was like housing the archbishop of Canterbury at the Vatican. Confined to a small space, the young boy seemed like a caged lion, as he paced the balcony gazing towards the snow-capped mountains of his homeland.

Because of his close association with the Dalai Lama, he was increasingly hailed as his successor.

Headlines like "The new Dalai Lama" and "The world's next top Lama" sparked intense speculation.

"Clearly a serious and exceptionally intelligent 15-year-old. Few can doubt his credentials as a future Tibetan leader," wrote the Observer in 2001. "He is the only … reincarnation, currently recognised by both the Chinese and the Dalai Lama. He could be the hinge on which relations between Tibetans and China swing in a new direction," claimed Newsweek in 2009.

This speculation put him at the heart of a political game with the Chinese who are determined to wrest control of Tibetan Buddhism after the passing of the Dalai Lama. The situation is further complicated by Indian government suspicions that the Karmapa may have been sent to India to destabilise Sikkim, which borders China, and which China claims as its own. The machinations of the Tibetan exile government to hang onto a charismatic figure capable of uniting the Tibetans after the demise of the aging Dalai Lama, stirs yet more political intrigue into the seething cauldron.

However, in the 900 years of their history the Karmapas have been entirely spiritual, even as gurus to the emperors of China in the 12th century. "For … 900 years," he told the Times of India in March 2009, "the Karmapa has been a very apolitical figure … who has concentrated solely on spiritual leadership, not involved in any way with governmental leadership. So I think it would be very difficult to change that historical pattern overnight and turn the role of the Karmapa into something more than strictly a spiritual teacher."

When I met him in November, he reiterated that his spiritual role required freedom of movement. "Traditionally the Karmapa travelled a lot to different places to meet the people who wanted to see him. Ever since I became the Karmapa I lost my personal freedom and choice but I have gained the opportunity of benefiting others. But sometimes I cannot play the role of Karmapa anymore. I don't have the right environment."

What distresses him is to be caught in the game of politics. The Indian government have offered no explanation for denying him permission to travel. When they cancelled the 2010 Europe tour, word leaked out that the tour was "too big and for too long". Nonetheless, simpler itineraries over shorter periods were also turned down without explanation.

Now for the first time he categorically disclaims any possibility of succession to the Dalai Lama. Clearly the strain was becoming intolerable.

"There is already a system in place for the Dalai Lama's regency. It is not necessary to already be an important public figure in order to become the regent, if one has the capability. I have the responsibility of being the spiritual leader of a lineage and I don't need extra responsibility. I cannot do beyond what a human being can do. The name "Karmapa" means the one who takes responsibility for all the buddhas' activities. This is overwhelming enough. I don't need more."

• A two-day ceremony to mark the 900th anniversary of the Karmapa lineage will be held in Bodh Gaya, India on 8 December