FOR ANYONE WHO only knows James Cagney as a hard-bitten gangster, squeezing grapefruit into his moll’s mush, or crying out, “Made it, ma! Top of the world!”, Yankee Doodle Dandy is a revelation. But Cagney had tap-danced since he was an angel with a dirty face, and as George M. Cohan, the songwriter behind patriotic chest-thumpers such as ‘Over There’ and ‘I’m A Yankee Doodle Dandy’, he got to strut and leap and cavort and talk-sing, decades before Rex Harrison, his way through a series of numbers. His crowning glory, though, comes at the end of the movie, which has been recounted by Cohan, in a series of flashbacks, to President Roosevelt. Story told, Congressional Gold Medal in his pocket, Cohan — now touching 70 — walks down a White…
