Complex sentence: Perceval's relationship with the Prince of Wales, who became Prince Regent, was far less cordial; the prince took personal offence when the Regency Bill introduced by Perceval in December 1810 placed restrictions on the regent's powers for the first year of the regency.
Split into simpler sentences: Perceval's relationship with the Prince of Wales, who subsequently became Prince Regent, was far less cordial. The prince was much offended when the Regency Bill introduced by Perceval in December 1810 proposed restrictions on the regent's powers for the first year of the regency.