The Holy Trinity Church of St.Andrews is located in the centre of the ancient town and has been rebuilt over the centuries on what was the site of a medieval church. It lies on Church Square and is bounded by South Street and Church Street.
The first church was built around 1144 on land to the south-east of the cathedral by Bishop Robert Kennedy, and dedicated in 1237 by Bishop David de Bernham.
The church then moved to its present site in 1410 after a donation of 180 feet of land by Sir William Lindsay, Lord of the Byres.
In 1547 it was the site of the first preaching in public of John Knox, and also his sermon on June 4th 1559 that led to the stripping of the cathedral and its ecclesiastical status.
The church was rebuilt by Robert Balfour from 1798-1800, and then restored to its former medieval appearance in 1907-09 by MacGregor Chalmers, with only the tower and spire on the north-west corner and parts of the arcade arches retained.
The church is in a medieval cruciform plan with nave, transept arms, chancel and aisles. A vestry and south east chapel, known as the Hunter Aisle were added in the 1907 rebuild. The church is built from tooled sandstone blocks, re-used from previous structures. The roof is of slate.
The main feature is is the tall L-plan tower on the north-west corner with two stone spires, one significantly taller than the other. Large metal and bronze clock faces adorn the tower.
The west end overlooks Church Square and is attached to the tower, featuring a double doorway that leads to the nave. The west gable is partially hidden at ground level by a parapet. The west end is dominated by a group of five tall, narrow, round-arched windows with stained glass. Below is a large Romanesque-style round-arched doorway.
The south side of the church faces the busy South Street and is dominated by the south transept and its massive gothic window with a round-arched doorway below. To the west of the south transept is the tall crow-stepped John Knox porch, built in the same position as the 15th century original, and is used as the main entrance. To the east is the single storey Hunter Aisle with a small entrance porch and a round-arched doorway.
The east side faces Church Street which links the two main thoroughfares of South Street and Market Street. This end features a very large gothic window. Attached to the north end is a side aisle or chapel.
The north side faces the narrower part of Church Square and features the north transept, known as the Playfair Aisle after Lord Playfair of St.Andrews. It has a group of three round-arched windows with a round-arched doorway below. Attached to the west is a gabled vestry.(source)