The Trinity Houses, built in 1772, are the visible continuation of an institution that predates them by at least two centuries, one of those cases where a building's purpose has outlasted every physical trace of its origins.

The Hospital of the Holy Trinity, in the medieval sense a hospital was not primarily a medical facility but a house of charity providing shelter and care for the poor, the elderly, or travellers, was founded by a man named Thomas Gregory, probably sometime in the mid-sixteenth century. The first surviving charter dates to 1587, by which point the institution had been granted the chapels of St Michael's and St Saviour's, the latter having stood close to the same site. Whether Gregory established the hospital before or after the Reformation complicated the question of its religious character, but the 1587 charter suggests it was formally reorganised in the later Tudor period, as many such foundations were. The charity evidently endured, since by 1772 it had resources enough to erect the current almshouses, and by some accounts it has continued functioning in some form to the present day. Archaeological testing carried out in the late 1990s found little to illuminate the earlier phases of the site, turning up nothing more than a single pit.