Who is John Baptist Cramer from The Great Pianists and what is their importance?

John Baptist Cramer is the name of a Clementi pupil called "Glorious John." He was born in 1771 in Germany and taken to London by his parents as a child prodigy. He debuted at ten and toured two years with Clementi playing his stringent classicism with purity and accuracy. Beethoven and Cramer played once in competition and Beethoven said Cramer was the only pianist of his time, and the "rest count for nothing." Cramer's piano playing got "dry, wooden and harsh" as he aged.