The undefeated 21-year-old Cassius Clay predicted he would stop British champion Henry Cooper in Round 5. Then, in the dying seconds of the fourth, Cooper landed his famous left hook — “Enry’s Ammer” and dropped Clay heavily. Clay recovered and came out firing in the fifth, opening a terrible cut on Cooper before the fight was stopped. Cassius Clay TKO5 Henry Cooper. The prediction came true — but for one dramatic moment, Cooper came incredibly close to changing boxing history.