Keir Starmer has long seemed wary of taking on big tech. But now he has vowed on his Substack to bring in new powers “to crack down on the addictive elements of social media”, to “stop the auto-play, the never-ending scrolling”. The spur for this is the need to tackle the harm that rich, careless Californians stand accused of doing to British children, but what’s striking is Starmer’s focus not on the content of social media, but the design. He’s not alone.  The European Commission is currently investigating TikTok on similar grounds. In the United States, the big social media companies are…