Complex sentence: In 1823, at the age of nineteen, after some foreign travel, he became a pupil of the architect Benjamin Dean Wyatt, who entrusted him with the superintendence of several of his most important works, including Apsley House and the Duke of York's Column.
Split into simpler sentences: In 1823, at the age of nineteen, after some foreign travel, he became a pupil of the architect Benjamin Dean Wyatt. He was entrusted with the superintendence of several of Wyatt's most important works, including Apsley House and the Duke of York's Column.