Complex sentence: Unlike Harrow East, it had always been won by the Conservative party until Labour's landslide in 1997 when a swing of 17.5% was the eighth highest swing in that election, and it was the safest Conservative seat to be lost to Labour.
Split into simpler sentences: Unlike Harrow East, it had always been won by the Conservative party until Labour's landslide in 1997. The swing of 17.5% was the eighth highest swing in that election, and it was the safest Conservative seat to be lost to Labour.