Complex sentence: It was listed on the London Stock Exchange and was once a constituent of the FTSE 100 Index and is part of the Aviva group, itself created by a merger of Norwich Union and CGU plc in 2000.
Split into simpler sentences: It was listed on the London Stock Exchange and was once a constituent of the FTSE 100 Index. It is part of the Aviva group, itself created by a merger of Norwich Union and CGU plc in 2000.