Complex sentence: Almost a year earlier he had called at Robert Catesby's home at Ashby St Ledgers and complained bitterly about James, who since succeeding Elizabeth he claimed had done little to fulfil his expectations.
Split into simpler sentences: Almost a year earlier he had called at Robert Catesby's home at Ashby St Ledgers. He complained bitterly about James, who since succeeding Elizabeth had done little to fulfil his expectations.