The show must go on. And it is a potential world tour being planned by a so-called 'hardcore' theatre collective on a converted cargo ship with a modern emissions-cutting sail to spread a message about the climate emergency.

An 18-metre-high eSAIL has been fitted on the Barcelona-based La Fura dels Baus theatre company's 1,160-dwt ship La Naumon (built 1979) ahead of a delayed tour of Spanish ports that the producers would like to expand around the world.

La Fura dels Baus made headlines some years back when its XXX Show had to be cleared by the UK Metropolitan Police's vice squad after allegations of live sex acts, which were untrue, but it could be argued a world tour would be even more hardcore for the performers.

However, they aim to demonstrate the emissions-reducing potential of the eSAIL developed by Spanish wind-assisted propulsion company bound4blue.

The rigid sail, equipped with a tilting mechanism and autonomous control system, is the largest yet fitted to a ship by bound4blue, which this summer installed a 12-metre version on a Pacific Ocean fishing vessel — the 342-gt Balueiro Segundo (built 1989).

The company claims on its website that it will also install two sails on an unnamed 120-metre-long bulk carrier that will undergo sea trials in the Atlantic.

The La Naumon installation was approved by DNV and done under the GREENing the Blue project co-funded by the European Union at the Astander shipyard in Spain according to the company.

"The installation can be performed afloat, like in the case of La Naumon, during a scheduled drydocking or during any port call, as the operation takes less than a day," bound4blue chief executive Jose Miguel Bermudez said.

In addition to helping to propel La Naumon, the sail will also act as part of the theatre's main stage.

Carlus Padrissa, creative director of La Fura dels Baus, said: “I imagine the eSAIL slowly rising to the magical wind of music, pyrotechnics and light.

"A trapeze artist with the wings of a butterfly, representing the transformation of renewable and circular energy, will fly anchored at its tip. It will be an immersive and global show that will provoke change and ignite consciences."

How La Fura dels Baus theatre company imagines shows on its ship, La Naumon Photo: La Fura dels Baus