He was primarily a church architect, building a considerable number of new churches and undertaking even more restorations. His church work was firmly in the Gothic revival mainstream of his time, rarely departing from the forms and decoration of the Decorated period, and lacks much originality or flair. His churches at All Saints, Reading and St Mary, Tyndalls Park, Bristol, are notably similar. His restorations often amounted to wholesale or partial rebuilding, and were seen by later generations as unnecessarily brutal; Sir John Betjeman was among St Aubyn's 20th-century detractors. St Aubyn also designed a number of country houses, mostly in a rather cheerless early Gothic style. The one whimsical building he is known to have designed is the clock tower in the grounds of Abberley Hall, c 1883. His greatest professional disappointment was his failure to secure the commission to build Truro Cathedral, which he lost by one vote to John Loughborough Pearson; his designs for the Cathedral were published in "Building News", 20 December 1878. His most notable achievement was the restoration of St Michael's Mount, described by Nigel Nicolson as: ""among the greatest achievements of 19th-century architecture"".