As Challis has already mentioned, this seems to have been a real historical incident which occurred in Chertsey, Surrey, UK and concerned a lady called Blanche Heriot whose lover was condemned to be executed when the curfew bell was rung.

The incident seems to have occurred during The Wars of The Roses, but there are some lyrics which place it later, during the Civil War. A curfew is still rung at Chertsey today - see more details here.