In what had been a heavily forested area, the site of Brentwood shows no evidence of either Roman or Saxon settlement, although the latter established themselves at neighbouring South Weald, which later became the parish on whose edge Brentwood was established. Brentwood was one of those towns that came into being on the road from Colchester to London (via Chelmsford), at the point where crossed by a road heading up to Chipping Ongar in one direction and down to the Tilbury ferry in the other; a road from Billericay also ran into the through-road. Brentwood thus benefited from the transit of pilgrims from the Midlands and East Anglia to the river crossing and on to Becket's shrine at Canterbury; before reaching Brentwood the road from Chipping Ongar passed through the hamlet of Pilgrims Hatch (meaning 'gate'), a name recorded in 1483. The crossroads marked the eastern end of Brentwood's High Street, which represented the extent of the town. At its western end the street was joined by a road from South Weald village to the north. The local name for the stretch of the London road just west of Brentwood may have been, as it was later, Brook Street, since it progressed to a crossing of the Weald Brook, a bridge being in existence there before 1276. By 1201 a leper hospital had been established about midway between the High Street and the brook crossing, at the corner of Brook Street and Spital Lane. East of Brentwood this through-road ran through Shenfield.
Two manors comprising South Weald feature in Domesday Book, though later we see more having been carved out. Most of the parish was, or came to be, in monastic hands; For example, South Weald manor, which lay to the north-west of Brentwood and included the parish church, belonged to Waltham Abbey from 1062. It was in 1176/77, just a few years after Becket's death, that we have the first written reference to Brentwood, whose name is indicative of a clearing made in the forest by fire, whether deliberate or accidental. Within the next few years William of Ockendon (whose name derives from his manor of North Ockendon, near Brentwood) gave his manor of Cocstede to the abbey of St. Osyth and the canons were authorized by the king (ca.1180) to clear forty acres within the royal forest for their private use; this suggests they planned to enlarge an existing clearing, perhaps in order to establish a market settlement, a project that did not necessarily proceed immediately but, when it did, it adopted the pre-existing name of Brentwood. All over the country areas of forest were being assarted cleared to make way for settlement, grazing land, or cultivation; for instance, contemporary with the foundation of Brentwood, the manor of Brendewode was being established in Lancashire by Whalley Abbey, likewise on what had been, in the reign of John, wasteland created by a fire within the forest.
That St. Osyth's project did go ahead at some point we may posit from the fact that, in 1221, the abbot obtained permission from the vicar of South Weald to build a chapel, dedicated to St. Thomas of Canterbury, in what was or would become Brentwood's High Street, for use both of the local populace and of pilgrims; not until 1440, however, was the chaplain authorized to perform the sacraments, and then only in emergencies, after the residents of Brentwood complained about the difficulty of getting to the parish church in bad weather. In November 1220 a Wednesday market was provisionally licensed to the abbot, to be held at his 'new stead' in Brentwood; this was renewed by Henry III in 1227, after he had come of age, when it was stated that abbey and canons were to hold the market in their town of Bois Ars. The terminology in these grants casts uncertainty on the character of the settlement the abbot had established; most probably, given ecclesiastical conservatism, it was more than a village, with settlers given the benefits of burgage tenure, but less than a borough, in terms of chartered privileges allowing any self-government.
At the same time as the market grant was renewed, Henry authorized a fair at the festival of St. Thomas not the commemoration of Becket's death, which was in December (not a prime season for fairs), but that of the transfer of his remains from the crypt of Canterbury Cathedral to an impressive shrine in a prominent place within the main area of the cathedral. This event, which had taken place in July 1221 (prime fair season), carried out with great pomp and ceremony, had both symbolic and pragmatic dimensions. On the one hand it was intended to re-emphasize the reconciliation of Church and State, after the disastrous rift in John's reign; on the other it catered to the Becket cult that had grown up over the previous half-century particularly among Londoners, but becoming widespread bringing valuable donations to the cathedral from pilgrims. Not only the date of the fair but possibly the weekday of the market was chosen in relation to St. Thomas. It was popularly (though incorrectly) believed that Tuesdays featured repeatedly in the significant events of Becket's life; in a location dedicated to the memory of the saint, to hold a secular event on Tuesday may have been felt sacrilegious, but the day following would have been acceptable. While the choice of day might normally have been governed, at least in part, by the competitive environment, there were no Tuesday markets in that part of Essex it was only later that nearby Billericay, Chipping Ongar, and Rainham would institute markets on that day, perhaps selected to avoid competition from Brentwood's Wednesday event. In fact, two market licences to Robert Walerand, lord of Rainham, are recorded in the Charter Roll on the same date in 1270: one for a Wednesday event and one for Tuesday; if this was not clerical error, which seems the simplest explanation, it may be that Walerand either quickly remembered that Wednesday could face a challenge from nearby Romford, which had an older Wednesday market, and he had the day changed. If there was any symbolic significance to Brentwood's market being on Wednesday, it was not important enough to prevent in 1252 a change of the day to Thursday, for which the abbot paid the king a mark in gold. It is unclear why the day was changed; competition seems not to have been the cause, for Billericay's Tuesday market had not yet been licensed.
It appears that St. Osyth's new town was laid out along only one side of Brentwood's High Street (probably the south), which fell within the area of land it owned a situation similar to that of Billericay. For in 1234 the lord of the adjacent manor of Shenfield, Thomas de Camvill (whose main holdings were in Kent, he holding Shenfield only through his wife's dower), obtained permission from the king "that he may have house plots established on his land at Brentwood, in his vill of Shenfield, on one side of the highway, just as house plots have been established by the abbot of St. Osyth's on the other side of the street, in his vill of Cocstede." [Calendar of Close Rolls 1231-1234, p.478; my translation]. Quite why Thomas needed royal licence is unclear, but it was probably related to the king's order to Richard II de Montfichet, Baron of Stansted and one of the larger landowners in Essex (whose manors included South Weald), to allow Thomas to proceed without obstruction; Thomas and his wife may have held Shenfield of Richard and been aware that Richard (who had a reputation for being troublesome and had market ambitions of his own he would licence two in Essex in 1253) had some objection. But more likely is that Thomas would have to clear some forest to make room for his tenement plots; Richard was the king's forester in Essex and, as such, had the duty to prevent any encroachments within the forest. It is uncertain if this was the Thomas de Camvill who died in 1235 (for there was at least one other contemporary of the same name), leaving underage heirs, whose lands were put into the wardship of Hamo de Crevequer, another Kent man and owner of a market in that county at Brenchley, which in 1230 was under pressure to move out of the churchyard and to a different day than Sunday, though this appears to have been successfully resisted for a couple of years. Thomas' intent was doubtless to capitalize on the abbey's foundation of a market town at Brentwood. It was not his first foray into that world, for a few years earlier, in 1227, Henry III had confirmed a grant by Henry II to Thomas' grandfather, Hugh de Camvill, of the manors of Westerham (Kent) and Fobbing (Essex) and, on the same occasion, Thomas acquired a licence for Wednesday markets at both and a fair at Fobbing; the market at Westerham, was the subject of a challenge from the earl of Gloucester on behalf of his nearby market at the borough of Brasted a challenge that does not appear to have been successful, perhaps because the earl had no licence for his market. These several royal grants cost Thomas a total of £20.
Like Billericay, Brentwood thus arose as a ribbon development along a wide through-road carrying commercial traffic, which later narrowed into Brentwood's High Street as a consequence of encroachment, underway by at least the fifteenth century. The White Hart Inn was one of the earlier culprits; its high-quality carpentry has prompted the suggestion it was built by the abbey to accommodate pilgrims [reported by Maria Medlycott, Brentwood - Historic Towns Assessment Report, Essex County Council,1999, p.6], though its location suggests it was targeted just as much at mercantile travellers. It can be calculated that the street's width at the time of Brentwood's foundation ranged from about 90 to120 feet; this changed west of where St. Thomas' chapel was erected, to a width of some 45 feet. Architectural fabric dating to the fifteenth century has survived in a number of buildings along the High Street, particularly in the stretch near the chapel. Further south and roughly paralleling the High Street is another street (now Queen's/Coptfold Roads) that might have originated as a service lane at back of the burgage plots; in the earliest known town map (1717) another lane is visible to the north, although more curving, perhaps to follow the contour of the terrain. The chapel would have stood in the centre of this wide street, throughout which market activities may have taken place. Somewhat west of the chapel the 1717 map shows what remained of the marketplace by that date; despite infilling of parts, it can still be perceived as having been a long space, with the High Street forming its north side and Back Street (now Hart Street) its south side. Four shops there are among properties acquired by a London spurrier and his wife ca. 1401, although disposed of a few years later, while about 1406 a salter of the same city acquired a tenement and two shops in Brentwood.
There is not a great deal of evidence of the economy of medieval Brentwood. It lay within an area that remained agricultural and pastoral up until relatively modern times, and doubtless its market dealt mainly in hinterland produce; we hear of a flesh-market and a corn-market, presumably areas within the marketplace. An ironmonger is recorded as holding a tenement there in 1280, but this was by right of his wife, and we cannot be certain they lived in Brentwood. The leather-working and cloth-making crafts are evidenced by references to a dyer and a skinner in the fifteenth century, but there is no reason to think those industries played a leading part in the local economy, although the existence in the sixteenth century of manorial officials for supervising the quality of leather goods suggests that trade continued to thrive. Services to travellers may have been, or become, more important; in the post-medieval period Brentwood developed into a coaching town, its inns, mostly on the High Street and the approach roads, furnishing a total of 110 beds by 1686.
But those same roads carried commerce and, by the fifteenth century, we find some London merchants considering it a good investment to own property at Brentwood, where, or with whose tradesmen, they must have done much business. For instance, in 1292 William de Winchester, a Brentwood taverner, acknowledged a debt in a London court, and in 1344 we hear of John Baker of Brentwood transacting an exchange even if this involved fencing stolen goods with William le Brewere at the latter's tavern in Cripplegate, London. Commercial relations between Brentwood men and Londoners is slightly better evidenced in the fifteenth century, from cases in the Westminster courts: Brentwood hosteler John Swaffham was sued (1422) by London mercer John Stratton for a debt of £7 12s.10d, hosteler John Richard for a debt of 40s. claimed by London grocer Robert Gayton (1438), and butcher Richard White of Brentwood was being sued (1439) for failing to deliver 100 quarters of charcoal to Geoffrey Boleyn, an up-and-coming mercer who would later serve as a London alderman and mayor. In records of the Court of Common Pleas we encounter in 1458 yet another Brentwood tavern-keeper, Thomas Brokke, described as a salter by occupation and probably a native of London, accused of defaulting on a debt of £19 8s. due London mercer Robert Stone; Stone argued that the previous year, at London, he had sold Brokke four barrels of wine and, a month later, leased him the White Hart inn at Brentford for a year, although Brokke denied everything. A Brentwood chapman, Thomas Abbot (alias Spicer), appears in a couple of Common Pleas cases in 1463, being sued by a London fishmonger for £7 15s.8d and by a city grocer, William Colchestre, for 52s.9d owed him for various spices, sugar, paper, yarn, linen, and canvas sold to Thomas in London (some conceivably for resale in Brentwood's market). The surname of the last-mentioned plaintiff points to another obvious commercial connection, illustrated by a lawsuit ca.1422 between two Colchester merchants, Thomas Bosse and John Brandon, and John Smyth of Brentwood in association with an Ipswich man; though we do not know the details, that the case was heard by the admiral's court suggests it involved maritime commerce.
It may have been a slight exaggeration for its residents to describe Brentwood, in a petition to the king in 1616, as a 'great market town'; but that it was a market town we need not doubt.