Complex sentence: Until 1997 it was the home of the Royal Postgraduate Medical School which then became part of Imperial College, the hospital continues to be a major centre of post-graduate medical study as part of the UK's first Academic Health Science Centre.
Split into simpler sentences: Until 1997 it was the home of the Royal Postgraduate Medical School, which then became part of Imperial College. The hospital continues to be a major centre of postgraduate medical study as part of the UK's first academic health science centre.