The speech, which is widely believed to have helped poison race relations in Britain, was made in 1968 at a time when rising levels of immigration were causing alarm.
In it Mr Powell cited a letter which he claimed summed up the fear and desperation of many white people in his constituency. It outlined the experiences of an elderly lady who complained that black immigrants had taken over neighbourhood, regularly abused her and even pushed excrement through her letter box. Mr Powell repeatedly refused to reveal her identity and numerous reporters sent to find her drew a blank.
As a result the suspicion grew that Mr Powell invented the mysterious old lady in an effort to promote his racist propaganda. But did he? Document investigates.