An Augustinian Priory and Hospital dedicated to St Bartholomew were founded in Smithfield in 1123 by Rahere (d.1145), a courtier of Henry I (c.1068–1135). Nothing now survives of the hospital.

The priory church was cruciform and may have had a tower at the crossing. It had a four-bay, aisled, vaulted, apsidal chancel and a seven-bay apse with three radiating chapels. The transepts were aisleless, but the S had an eastern chapel added in the 13thc. (Webb 1921, II, 5; pls. XLIV and XLVa). The aisled nave was of ten bays. There were galleries above N and S chancel and nave aisles, and a clerestorey.

The first phase of construction, comprising much of the chancel, the galleries, and possibly the clerestorey was carried out under Rahere. A set-back (of c.6.5 cm) visible in the N wall of the chancel appears to mark a halt in construction, and a subsequent error in the alignment of continuing building work (Webb 1921, II, 8).

The crossing, tower, transepts and at least part of the nave were built in the priorship of Rahere's successor, Thomas (d. 1174), between 1144 and 1174. The chancel arcades may have been completed at this time. Additional small bays with carved capitals were inserted into the chancel gallery bays and a clerestorey was built (or rebuilt) above.

The nave was completed in the 13thc. This involved removing and adapting some of the easternmost 12thc. work so only the first bay of the 12thc. N and S arcades survives. 13thc. work intrudes into this. A tower, above what was the first bay of the S nave aisle, was built in 1628.

The base of a 13thc. shaft may be seen on the exterior NW corner of the church where the nave arcade stood. A small section of masonry from the 13thc. N nave wall survives in what is now the church yard, and at the site of the W end traces of 13thc. work may still be seen. These now lie below, and are obscured by, a galleried, half-timbered structure. When the church was completed in the 13thc. it would have been c. 310ft in length. The chancel E chapel, and the crypt beneath, was rebuilt in 1335, increasing the church length to c.349 ft. Webb proposes what he believes to be physical and documentary evidence for at least one W tower (Webb 1921, II, 67).

The S apsidal chapel (dedicated to St Stephen) survived until 1879, The N chapel (dedicated to St Bartholomew) was rebuilt at the end of the 14thc., but to the W of the original N chapel, although the N chapel entrance may still be seen. The E chapel (Lady Chapel) was rebuilt in 1335. Excavations carried out in 1913 revealed the original 12thc. apsidal E chapel (Lady Chapel) and showed that the S chapel originally had two apses. The N chapel would presumably have been the same (Webb 1921, II, 4; 5; 95).

In the early 15thc., the easternmost piers of the chancel apse were demolished and a straight E wall inserted in front of piers 2 and 7. The floor of the chancel was raised at this time. The clerestory was rebuilt, as was the cloister. Settlement of the NE pier of the crossing meant that the N and W arches also had to be rebuilt at this time. The arch capitals and corbels were replaced as was the base of the NE pier.

After 1505, the then prior (William Bolton) built a residence at the E end of the church, building a square E end in the S ambulatory and annexing the S gallery for his private use as a chapel, building an oriel window in the second bay.

The nave was dismantled after the priory was dissolved in 1539 and the chancel retained for parish use. The N gallery above the chancel was used as a schoolroom from the later 16thc. The N transept and chancel chapels were probably demolished at this time (RCHME, 123). The S transept survived, and was in use as a vestry in the second half of the 19thc.

The E chapel (Lady Chapel) became a house and later a lace factory and N and S galleries and many of the remaining priory buildings were also adapted into residences or workplaces. A smithy occupied the N transept until the late 19thc. and the S gallery, from the 17thc. to 1830 was a Non-Conformists' meeting house. A fire in 1830 severely damaged the S side of the church, and discoloured burnt stone is visible on the S face of the 12thc. stonework in the S gallery.

Two major restorations were carried out in the 19thc. The first in 1863 by Hayter Lewis and William Slater and the second, begun in 1884, by Aston Webb. The first restoration lowered the floor to its original level and reconstructed the two apse piers, removed in the early 15thc. According to a groundplan of the church drawn by Aston Webb, they also rebuilt much of the fabric of the piers in N and S aisles (Webb 1921, II, pl.XVI; 14). Aston Webb rebuilt the arcading at gallery and clerestorey level at the E end of the apse (using some original material) the Lady Chapel, and the sanctuary arch. The S end of the S transept was rebuilt in 1891 and the N transept in 1893 (Webb 1921, II, 14). The porch and facade are also by Aston Webb and date to1893.

Of the 12thc. features much of the original apsidal chancel survives, along with the crossing, part of the S transept, the first bay of N and S nave arcades and the S nave doorway to the cloister. Romanesque sculpture is found throughout the church and on a large number of loose fragments held in the S aisle gallery.

The earliest parts of the church are of ragstone, with ashlar dressings. Later additions are in brick and dressed flint rubble.

St Bartholomew, Smithfield was the third Augustinian house to be founded in London. The first being St Mary Overie (Southwark Cathedral) founded in 1106 and the second, Holy Trinity, Aldgate, founded in 1107. Land was granted by Henry I in 1123 to found the priory and hospital. The Augustinian order was particularly popular in the reign of Henry I and he and his entourage were responsible for the foundation of many houses.

The founding of the Priory and Hospital by Rahere is recounted in The Book of the Foundation (British Library Vespasian BIX) followed by an account of his life, the life of Prior Thomas and the miracles recorded at the priory during this period.

The first charter of privileges was granted in 1133 by Henry I, protecting the status and possessions of the priory (Webb 1921, I 60-62). An undated charter of Henry II confirms the grants made by Henry I, and lists the priory's extensive possessions (Webb 1921, I 101-2). These grants were confirmed by successive monarchs until the Dissolution. Webb's two-volume study recounts in full the history of the abbey, including transcripts of most important texts and charters (Webb 1921, I and II).

At the Dissolution, St Bartholomew was assessed as being the second most wealthy monastery in London, with a net income of £693. (Webb 1921, I , 4)

St Barthomew was one of the last 12thc. churches in England to have an apsidal E end and Webb suggests that Rahere was inspired by Gundulph's plan of St John's chapel in the Tower of London (Webb 1921, II, 7). However, comparisons are more usually made with the apsidal E end of Norwich cathedral, which shares the feature of double-apsed, apsidal chapels (Franklin 2006, 112) These two buildings contain the only surviving evidence of such chapels in England. Norwich was innovative in its architecture, but St Bartholomew, following a similar pattern some thirty years later, is not judged to be so, although a tentative suggestion that towers may have stood at the angles between transept and nave and transept and crossing has been made (Franklin 2006). Pevsner suggests that the pointed arches of the crossing may be the earliest to appear in London (Pevsner 1957, 135).

The richness of the 12thc. sculpture of the priory is demonstrated not just by the sculpture still in situ, but by a large number of fragments discovered during the 19thc. restorations. An early 15thc. passageway in the S clerestory also had a number of fragments of Romanesque sculpture built into its walls which are among those now in the S gallery (Webb 1921, II, pl. LXVI; 40).

As would be expected, many of the features of the carved stones find parallels in the carved stones in situ. For example, the scallop capitals, vi and xxxi, have the same billet-like mouldings between the cones and similar angle detail to those of the passageway openings in the crossing; the former nave S aisle S respond pier, and the S nave doorway. A further example is the lozenge voussoirs xvi-xvii which are paralleled by those on the jambs and arches of the spandrel openings.

A feature that occurs on a number of the fragments is a type of round billet connected by a fine roll/thread which is found on arcading fragments (xlii-xliv); a springer (xxxii); a group of chevron voussoirs (xxxvi-xl); and a section of label (xli). The same feature may be seen on the label on the arch of the first bay of the original N nave gallery.

Both of the above occur on features asssociated with Thomas' build.

Some of the carving on the loose fragments is of very high quality, especially the voussoir groups (xx)-(xxiv) and (xxvii)-(xxx). The latter group is exceptionally finely carved, with deep undercutting. Neither group has ready parallels among the in situ sculpture.

A voussoir in the collection of the Victoria and Albert Museum (A17-1916), of the same type as (xxvii)-(xxx) has been compared to carvings from the W doorway of the Temple Church, London and to St Peter Dunstable (Beds), noting however, that the Smithfield voussoirs are less undercut and more 'Romanesque' (Williamson 1983, 94). The early 1170s was suggested as the likely date for these fragments when compared to the date of c.1190 that had been proposed for Dunstable and c. 1180-85 for the Temple Church (Zarnecki 1975, 248 refering to Marks 1970). However, more recently, an earlier date, of c.1170 (Thurlby, 2001, 165), and even more recently of c.1160 has been proposed for Dunstable (pers. comm. Neil Stratford 2005), which suggests that an earlier date might also be considered for the Smithfield voussoirs. The sophisticated undercut sculpture of these fragments suggests that they are likely to be from the second building campaign and an earlier date would still sit comfortably within Thomas' priorship. There is no way of identifying the original location of individual fragments with certainty. Webb suggests that such fragments may have come from the 12thc. clerestory, and Williamson also suggests that they could be from windows, or from cloister doorways.

The quatrefoil panels in the spandrels of the crossing have been compared with sculpture at St Albans (Herts) and a fragment from Missenden Abbey (Bucks), an Augustinian abbey founded in the 1130s (Thurlby 2001, 166).

The cat head found in the SW angle of the S transept just below the level of the crossing capitals, is unusual, in that normally such features are in the form of shaft-swallowers rather than simply corbels, as at Great Shefford (Berks) (pers. comm. R. Baxter 2012).

There are many fragments which have an early appearance, and which may date from the first phase of building, such as capitals (i) and (ii). These are block capitals. (i) has traces of carving on the visible face but (ii) has no surviving carving (the capitals were too heavy to turn over without risking damage to them).

As mentioned above, a carved voussoir now in the collection of the Victoria and Albert museum (A17-1916) is of the same type as voussoirs (xxvii)-(xxx), and the museum holds a second voussoir (A18-1916) which is also recorded as having a counterpart among the loose stones at St Bartholomew's. However, there is at present no trace of this second carved stone.