Complex sentence: The original 2010 raised tomb design proposed by Langley`s Looking For Richard Project and fully funded by members of the Richard III Society had been launched by the Society on 13 February 2013 but was rejected by Leicester Cathedral in favour of a memorial slab.
Split into simpler sentences: The original 2010 raised tomb design had been proposed by Langley`s "Looking For Richard Project" and fully funded by members of the Richard III Society. The proposal was publicly launched by the Society on 13 February 2013 but rejected by Leicester Cathedral in favour of a memorial slab.