We live, it cannot be doubted, in an age obsessed with celebrity. The very word now has the power of a charm. It can be added to any feeble project to give it the sparkle of glamour and excitement. Or so, at least, it is hoped. From the faltering beginnings of Celebrity Squares we have very quickly reached the saturated coverage of Celebrity Love Island, Celebrity Big Brother, Celebrity Wrestling, I’m a Celebrity Get Me a New TV Contract. And now, at Tate Britain, we are being offered Joshua Reynolds: The Creation of Celebrity.