Complex sentence: Hastings line, and this caused very high wheel forces at track irregularities; this may have been the reason why this particular train derailed, due to the derailing ramp that was formed as the third coach passed over.
Split into simpler sentences: Hastings line, and this caused very high wheel forces at track irregularities. That may have been the reason why this particular train derailed, due to the derailing ramp that was formed as the third coach passed over.