Gather five practitioners together in brightly lit room with hard floors. Ask them about what yoga means to them, and you'll get five different, yet completely authentic, answers.

“For me, yoga's like eating, sleeping, breathing. It's something that I have to do,” explains James, as he perches calmly on his mat.

For Alaric, it's also about something more than daily life. “As an Iyengar teacher, it's about refinement of consciousness, with the body as tool.” His bright blue eyes radiate intensity. “The body is also the doorway to discover and experience mystical phenomena.”

Sharing the mat with Alaric is Suzanne. “It's a form of healthcare, it's an idea of union with the divine. One can draw from this rich tapestry to create different understandings of yoga.”

Modern yoga is a global phenomenon. It’s also big business – many of the major schools or styles of yoga are transnational organisations selling classes, equipment, books and videos for their systems. There has even been a (failed) attempt to copyright a yoga system.

At the same time, modern yoga systems insist on their continuity with ancient practices, drawing on the authority of an apparently unbroken tradition going back thousands of years.

Most people are vaguely aware that the origins of yoga are connected to ancient India. The postures (asanas) and breath control (pranayama) we do in our weekly yoga class are often given as translations from Sanskrit names such as adho mukha svanasana – downward facing dog.

But how did a tradition with ancient roots in the Indian subcontinent end up as a weekly yoga class in places as far afield as London and Los Angeles?