[1] The Decorated/Early English-style church is distinguished by its opulently decorated interior and its layout on a difficult town-centre site, chosen after another location was found to be unsuitable.

Improved transport links, putting it within reach of daytrippers from London, made it an extremely popular seaside resort and a "wealthy, successful town of strength and confidence".

[4] The subsequent development of Hastings outgrew the compact valley around the Bourne stream on which the Old Town was centred, and moved further and further west as more land was required.

[5] Soon afterwards, James Burton's high-class planned town of St Leonards-on-Sea, even further west, attracted more people to the area, and the gap between it and Hastings was soon filled.

[4] Local philanthropist and church benefactor Countess Waldegrave gave £1,000 (£138,300 in 2025))[7] to help pay for its founding, and Samuel Sanders Teulon was commissioned to design the building.

He had recently submitted plans for a large house in Hastings, and had designed and executed churches at nearby Rye Harbour and Icklesham.

[8] A piece of land on the north side of Cambridge Road, above Holmesdale Gardens (approximate location 50°51′21″N 0°34′30″E / 50.8558°N 0.5751°E / 50.8558; 0.5751), was donated by the Earls Cornwallis; but soon after work started, a landslip revealed the site to be unsafe.

[7] She was so concerned about the displacement of poor people from the former wasteland area that she paid for a new church to be built in St Leonards-on-Sea, where many had been forced to move.

[11][13] Next to it, on the south side, space above the porch was intended to hold a tower and spire, but because the church cost so much to build neither feature was ever added.

[8][13][14] Between 1889 and 1890, the chancel arch was given intricate carved decoration by sculptor Thomas Earp, and a craftsman from Ghent provided an ornate rood screen.

[19] Samuel Sanders Teulon had to fit his design for Holy Trinity Church into the difficult, restricted town centre site[13] (described by Nikolaus Pevsner as "crazy"),[14] and the layout is consequently very unusual.

[11] The nave is of six bays and has a south aisle, a chancel with an apse, a vestry with a conical roof, and a porch formed from the base of the intended tower.

The north side, facing Trinity Street, is divided into six cross-gabled bays, each with a three-light window with similar tracery.