John Lennon and Yoko Ono appear onstage in a white bag

As part of the Underground Christmas Party, a happening taking place at the Royal Albert Hall in London, John Lennon and Yoko Ono appeared onstage inside a large white bag.

The event was held by the Arts Lab, which attempted to challenge audiences, to encourage them to become active participants rather than passive consumers.

The couple’s 30-minute conceptual performance was titled Alchemical Wedding. The bag was, they explained, to ensure “total communication” with the audience. The following year the concept was reintroduced by the pair as Bagism, an attempt to satirize prejudice and stereotyping.

Lennon and Ono sat on the side of the stage as other poets and musicians performed at the event. When their time came, they entered the bag, remaining there while a man played a flute.

Lennon and Ono initially sat cross-legged inside the bag. They moved only twice during the performance, to lie closer to the floor.

During the performance a protestor ran to the stage, holding a banner about the British government’s involvement in the Nigerian civil war. “Do you care, John Lennon? Do you care?” the protestor shouted at the couple.