When the Olympic Flame arrived at the Tower of London last Friday, Mayor of London Boris Johnson joked that, as King Henry VIII had discovered, the Tower was "the perfect place to bring an old flame". An old flame is a person you loved romantically in the past and the Mayor was referring to Henry's second and fifth wives, Anne Boleyn and Catherine Howard, who were both imprisoned in the Tower prior to their execution. The ghost of Anne Boleyn is said to haunt the building.
You can also have a "new flame" or "latest flame", as in the Elvis Presley song:
Elvis Presley - His Latest Flame