Complex sentence: The class was introduced in 2002 to serve the tidal reach of the River Thames, which had not previously been covered by an RNLI rescue service, as a result of a much delayed enquiry into the Marchioness disaster in 1989, in which 51 people died.
Split into simpler sentences: The class was introduced in 2002 to serve the tidal reach of the River Thames, which had not previously been covered by an RNLI rescue service. This was as a result of a much delayed enquiry into the Marchioness disaster in 1989, in which 51 people died.