Greenpeace UK is sending its vessel Arctic Sunrise south west in the coming weeks to begin a “barrier” at South West Deeps, 200 miles off the Land’s End peninsula.

The organisation said it is pushing ahead with its third boulder drop – having previously dumped them on “marine protected areas” off Brighton and Dogger Bank, 80 miles off Yorkshire.

Despite the name, marine protected areas are still open to large-scale trawlers that drag nets along the bottom, destroying much of what is in their path.

Greenpeace may have been emboldened after a Judge criticised the Marine Management Organisation (MMO) for taking a private prosecution against them for dropping boulders off Brighton in a similar operation to protect marine life.

In January Judge Edward Bindloss said the case was not in in the public interest and it “touched on the absurd” that it was taking place.

After his intervention, the MMO offered no evidence – sparking an angry response from the “voice for UK fishermen”, the York-based National Federation of Fishermen’s Orgnisations, who warned that it would send a signal to Greenpeace “to carry on their vigilantism”.

According to Greenpeace, the South West Deeps is one of the most heavily fished marine protected areas in the UK.