Complex sentence: The firm is listed on the London Stock Exchange and a constituent of the FTSE 250 Index and was the founder and former sponsor of the highly prestigious Booker Prize (originally the Booker--McConnell Prize) for literary fiction, which was established in 1968.
Split into simpler sentences: The firm is listed on the London Stock Exchange and a constituent of the FTSE 250 Index. The company also founded and was previously a sponsor of the highly prestigious Booker Prize (originally the Booker--McConnell Prize) for literary fiction, which was established in 1968.