Complex sentence: Marks'most important patron was Hugh Grosvenor, 1st Duke of Westminster and he worked on decoration for the duke's house, Eaton Hall, Cheshire, between 1874 and 1880.
Split into simpler sentences: Marks'most important patron was Hugh Grosvenor, 1st Duke of Westminster. Marks worked on decorations for the duke's house, Eaton Hall, Cheshire, between 1874 and 1880.