Tall for his time at 6'4", he was educated at Trinity College, Dublin, and afterwards he lived in London, where he was a close friend of the poet Thomas Campbell with whom he helped to found the Literary Association of the Friends of Poland, of which he was secretary.
This passage describes a person who is tall for his time (6'4"), educated at Trinity College, Dublin, lived in London, and had a close friendship with the poet Thomas Campbell, who helped him establish the Literary Association of the Friends of Poland, which he served as secretary.