Complex sentence: She became the first Briton to win an Olympic swimming gold since Lucy Morton in 1924 and the first athlete in any sport to hold Olympic, European and Commonwealth gold medals at the same time.
Split into simpler sentences: She became the first Briton to win an Olympic swimming gold since Lucy Morton in 1924. This led to her being the first athelete in any sport to hold Olympic, Commonwealth and European Gold medals, at the same time.