He was educated at Bedford School.
Many of their major commissions were church restoration works, most famously for Llandaff Cathedral. In 1871 he submitted a design in a competition for Holloway Sanatorium. C.F.A. Voysey was articled as a pupil of Seddon in 1873.
In 1904 he was Diocesan Architect for London and designed a gigantic Imperial Monumental Halls and 168 metre tower to be added to Westminster Abbey.
lieutenant was supposed to restore the dominance of Westminster Abbey over the surrounding crowd of towers and monuments. However, the cost of construction was prohibitive and it remained unbuilt.
He was also a prolific designer of furniture, metalwork, stained glass, tiles and ceramics.