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The group has drawn attention, criticism and jail terms for protests ranging from throwing soup on Vincent van Gogh's Sunflowers and spray-painting Charles Darwin's grave, to climbing on M25 gantries.

The auditorium is being redeveloped, reinstating the back wall, new control room, upgraded lighting system in the gantry, and a new ventilation system.

The protests saw about 45 protesters climb onto gantries over the motorway for four successive days, at times bringing the motorway to a standstill.

For four days, Hallam and more than three dozen other activists climbed a gantry and thereby blocked traffic in London’s critically important M25 motorway.

They are known as gantry cranes - meaning they straddle and overlook their workspace - and are of Krupp Ardelt design, modified to meet Harland and Wolff's special requirements.