St. James's is in many ways the finest of the group of four closely similar churches designed by Sir Christopher Wren for building on large open sites, the others being St. Anne's, Soho, St. Andrew's by the Wardrobe, and St. Andrew's, Holborn. Wren's own regard was such that he singled out St. James's for description and commendation in his letter 'Upon the Building of National Churches'. There he wrote: 'The Churches therefore must be large; but still, in our reformed Religion, it should seem vain to make a Parish-church larger, than that all who are present can both hear and see.

The foundation stone was laid on 3 April 1676 by the Earl of St. Albans and the Bishop of London. This evidence about the date at which the church was begun is supported by the fact that in 1677 John Cock, plumber, was asked to perform the lead work for the church, rectory and steeple, and claimed later that he had done work to the value of about £900 in 1677, 1682, 1686 and 1687.

The cost of the body of the church was about £7000, a sum provided by the Earl of St. Albans and the inhabitants of the future parish. The Earl, whose beneficence was recorded by the carving of his arms on the keystone block over the west door, over the then north and south doors and on the plaster enrichments of the ceiling, died at the beginning of 1684, before the church was consecrated.

The predominantly wealthy and influential congregation of the church was not a docile one, and frequently made unreasonable demands on the vestry. One such demand came from the Earl of Clarendon who wanted to make a door in the churchyard wall 'for the Convenience of his Lordpps. Beere, Wine and Coles to be brought that way into his house.' Tactfully, the vestry refused the request on the grounds that it would bring down 'Ecclesiasticall Censure'. Members of the congregation also altered the pews to suit their convenience and sent carpenters to put up benches, and rails on the seats.

The interior of the church, which had been admired for its beauty by contemporary writers, owed its brilliancy not only to the richness of the congregation's dress but also to the whiteness of the walls, the gilded fittings, and the handsome furniture, all illuminated in winter by scores of candles.

During the eighteenth century the church remained substantially unaltered. Repairs were carried out in 1751 when 'Mr. Timbrell or any other prominent surveyor' was ordered to be consulted, and the workmen employed included Williams Ludbey, mason, John Ludbey, carpenter, Samuel Ludbey, bricklayer, and William Pickering, painter. John Ludbey lent £400 to the vestry towards the cost of the repairs..

The first major alteration of the fabric was made at the beginning of the nineteenth century. A faculty was obtained in 1803 and in 1803-4 alterations were carried out under Thomas Hardwick's supervision. The north doorway was replaced by a window; a robing room was built on to the east end of the church; the rector's pews in the chancel were taken down to make room for a new pulpit and reading desks; seats for the poor were put in the middle aisle, and new staircases built to the galleries. The north and south arches in the first stage of the tower were bricked up and the west and east arches fitted with folding doors.

In 1856 the south doorway was removed and two vestibules were erected in the angles between the tower and west face of the church. These were linked by a continuous ambulatory formed by the reopening of the north and south arches of the tower, thus providing access from the north and south into the body of the church at the west end. The interior staircases to the galleries were removed, new stone stairs being built within the vestibules, and the extra room thus provided was used to increase the number of free pews.

In 1878 the rector, J. E. Kempe, made further alterations to the church to commemorate his tenure of the living for a quarter of a century. The pews at the east end were cut down and converted into open seats and the east end fitted up 'to give it more the aspect of a chancel'. The vestibule under the tower was made into a baptistery; the door in the west wall of the tower was shut up and a window inserted above it.

In 1940 a bomb, which destroyed the rectory and vestry, fell in the churchyard, and incendiary bombs destroyed the spire and most of the roof. The building was restored in 1947-54 by Messrs. Richardson and E. A. S. Houfe, architects, under the personal direction of Sir Albert E. Richardson; the work was carried out by a Cambridge firm, Messrs. Rattee and Kett.

For safety's sake, the height of the tower was reduced in 1955.

The leaning of the steeple in 1687 caused alarm for the safety of the roof over the body of the church, which was perhaps more endangered by neglect. In 1693 Sir Christopher Wren sent a message to the churchwardens, desiring them to take care of the roof 'to preserve it from wet'. He was much concerned about the preservation of church roofs, for which he thought 'good Oak is certainly the best; because it will bear some Negligence. It was, however, built out of fir.

The central part of the roof was destroyed in 1940 by incendiary bombs, but it was found possible to save the fir timbers of the roof over the aisles. The present ceiling was reproduced by Messrs. Eaton Contractors Ltd., by using existing measured drawings and pieces salvaged after the fire. It is constructed of fibrous plaster and the ornaments were cast in the church itself; four thousand books of gold leaf were used to gild the plasterwork.

In July 1685 the vestry ordered curtains to be provided for the windows and green curtains continued in use in part of the galleries at least until 1822. In 1821 the windows in the south gallery were ordered to be glazed with ground glass to keep out as much sun and light as possible, so that curtains might be dispensed with on that side of the church. Ground glass was also inserted in the lower windows on the north side later in the same year.

Wren evidently preferred an uncurtained light, at least at the east end. In 1693 the removal of the curtain over the east window occasioned some disagreement amongst the vestrymen; 'Some were for putting it up [again] others for bricking up the Window halfe way and some for letting the Window be as it is.' Wren, whose advice was sought, considered that 'it was best to let the Window be without any Curtaine'.

In 1743 the oval windows at the east and west ends were stopped up and at the time of the repairs to the church in 1764 Goreham prepared designs for ornamental mouldings to go over them. The vestry approved these and ordered that they should be executed 'as near similer to the other windows as possible'. A new window was substituted for the north doorway in 1803 and in 1856 a similar window was inserted in place of the south doorway.

In 1810 several 'respectable' inhabitants suggested that the east window should be filled with painted or stained glass. The vestry did not object, provided it was paid for by voluntary subscription, but only sufficient funds to pay for the upper part of the window were promised. The subject chosen was the 'whole History of the Transfiguration', and in 1813 Joseph Backler agreed to execute the work and fix ground glass in the lower part of the window for a sum of not more than £1250, or to complete the whole window for £2000.

By 1857 two more windows by Wailes had been put up, furthering the intention to fill in all the gallery windows with stained glass. Another two were put in by Messrs. Ward and Hughes by 1888, one commemorating the church's bicentenary. On the restoration of the church Crown glass was put in all the windows except the east, where stained glass, designed by Christopher Webb, and depicting scenes from the life of Christ, was inserted in 1954.

The body of the church, contained by a brick wall some three feet thick, consists of a five-bay nave about 37 feet wide, flanked by galleried aisles, making the total internal width some 67 feet. The east and west walls are broken by shallow projecting bays, of about the wall's thickness, giving the nave a total inside length of 87 feet 6 inches. Incorporated with the west wall is the brick tower shaft, externally square and internally octagonal in plan, its first stage originally formed as an open porch.

The present arrangement of the church floor follows, in general, that in use after 1878. The easternmost bay of the nave serves as a chancel, raised one step above the general floor level and flanked by stalls. A wide cross-gangway separates this chancel space from the handsome new oak benches, all facing the altar and spaciously set out to form two blocks in the nave, with a wide central gangway, and one block in each aisle. The west bay of the north aisle now serves as the baptistery, and the east end of the south aisle is arranged as a chapel.

The simple utilitarian exterior of the church, as contrasted with the richness and elegance within, has always been adversely criticized, though seldom so forcibly as when Joseph Gwilt called it a 'barbarous brick-cased and ill-shaped pile' and likened it to the toad which is 'ugly and venomous, yet wears a precious jewel in its head.' The jewel, of course, being the universally admired interior.

In St. James's Wren created one of his most elegant church interiors, with slender plain-shafted Corinthian columns raised on square piers, forming the lightest of arcades between the nave and the galleried aisles and helping to support the ingeniously designed roof trusses. On each side five almost equal bays are formed by six piers and columns, the first and the last standing free but in close proximity to the breaks in the east and west walls.

In 1684 Sir Robert Gayre, who lived in a house in Jermyn Street, gave to the church 'the Altar, and all the Furnitur; and Plate'. To commemorate his gift his arms were ordered to be put up in the church. These have disappeared but in 1954 a descendant gave the painting on the wooden lunette above the vestry door which records his arms and his death in 1702.

The altar was enclosed by a 'strong and graceful Rail and Banister of white Marble, artfully carved.. The four marble panels set in the railing were taken away in 1821 because of their decayed state. An estimate for their repair, together with the railing, was produced in 1820 by Mr. Hardwick but it being thought too costly he was asked to provide estimates for a similar railing in brass or wood. 'Best bronze' was eventually chosen, and Parker made the panels for £220 10s.

In 1846 the limewood carvings had also become very dilapidated and they were restored by George Lock and G. Kent of Leamington, using 850 new pieces. The altarpiece was painted and grained in imitation of walnut and varnished during alterations made to the church in 1866. In 1878 the marble enclosure was raised and enlarged.

Towards the end of the nineteenth century painted panels were inserted in the altarpiece under the pediment, one depicting the Last Supper, and others, in the flanking faces, portraying the Apostles. They survived the war, but were not reinstated.

The Act of 1685 allowed for part of the rate collected in the parish to be used to provide the church with one or more bells. The bell which now stands in the churchyard is inscribed 'William and Philip Wightman made me 1686', and is presumably the bell which was named on St. David's Day, 1687. Probably as a result of the cracking of the tower the bell was taken down temporarily but it was rehung in October 1688, with a little bell which had been borrowed. The Act of 1696 which empowered the parish to raise rates for payment of the debts for building the steeple, prohibited the hanging of more than two bells.

Shortly after its erection the steeple was embellished with a clock given by Henry Massy. This was replaced in 1764 by a clock made by Aynsworth Thwaites who received £100 and the old clock in exchange.

The church was originally lit by two brass and iron candle branches hung from the ceiling, which were made by Mr. White, founder. Supplementary lighting was provided by brass sconces and by iron candlesticks fixed to the pews. At an enquiry held in 1740 it was shown that over a hundred candles were used on winter Sundays.

In 1835 the vestry considered lighting the church with oil but this proposal was apparently abandoned in favour of gas-lighting by the Equitable Gas Company in 1837. The heat from the bronzed gas brackets and standards made the atmosphere of the church too oppressive, however, and most of them were removed in 1866 when two sun-burners were installed in the ceiling by Messrs. Strode. Vertical pew lights were installed when the church was restored.

The grant from the Crown to Thomas, Lord Jermyn, in 1684 included the freehold of two pieces of land adjoining the church site. One piece, roughly equal in extent to the site of the church, lay to the west, fronting Jermyn Street. It became known as the 'green' churchyard and originally gave access to the west door and outside gallery stairs by means of gates in its east and south walls.

The other piece of land lay on the north side of the church, but was separated from Piccadilly for many years by a row of buildings. These included the rectory, two houses on property not belonging to the parish, the watch house and houses and stables belonging to the rector as part of his endowment. Between the watch house and the rector's property stood the gates which gave access to the north entrance of the church.

The churchyard was first lit by patent lights in the winter of 1688-9. In November 1688 the churchwardens were asked to install 'such a Light or Lights as are used in Jermine Streete' on the south side of the church 'to light along the Church yard Wall there and front of the Church'. The wardens entered into an agreement with Edmund Heming and John Bulteel, representatives of 'the Copartnership of the New Invention of Lights' for two 'great lamps' to be put up on the north and south side of the church. The initial fine was £9 for installation and the rent for a five-year period was fixed at £4 per annum, the wardens being responsible for the provision of oil and for lighting the lamps.

The gates and railings on the south side of the church appear to date from about 1800. They are of good design, though simple, with vase-headed standards and trellised panels that originally terminated in lamp-holders.

Few of the memorials in the churchyard are now decipherable.