“Huh. As I suspected. The vaunted optimism of Shrigley’s thumbs-up to Britain’s glorious future is undermined by the deathly black hue of his appendage. Then there is the surreal monstrosity of the hugely deformed thumb. At seven metres high this is the tallest sculpture ever put on the plinth and, while that may seem the kind of statistic tour guides reel off, it has genuine relevance to how it works on a square that is also home to Nelson’s Column.”