Complex sentence: Since the cause of the mistake could not be established with certainty, a new headstone was placed in 2009 bearing the inscription "Believed to be Sergeant William Sharpe", and the CWGC has updated its database.
Split into simpler sentences: Since the cause of the mistake could not be established with certainty, it was decided to have the grave marked with a new headstone bearing the inscription "Believed to be Sergeant William Sharpe". The new headstone was placed in 2009, and the CWGC has updated its database.