Vacarius was probably a guest in the court of Archbishop Theobald where Thomas of London and John of Salisbury were already busy with the study of the Civil Law. But when he opened lectures on it at Oxford he was at once silenced by Stephen, who was at that moment at war with the Church and jealous of the power which the wreck of the royal authority was throwing into Theobald's hands. At this time Oxford stood in the first rank among English towns. Its town church of St. Martin rose from the midst of a huddled group of houses, girded in with massive walls, that lay along the dry upper ground of a low peninsula between the streams of Cherwell and the Thames. The ground fell gently on either side, eastward and westward, to these rivers; while on the south a sharper descent led down across swampy meadows to the ford from which the town drew its name and to the bridge that succeeded it. Around lay a wild forest country, moors such as Cowley and Bullingdon fringing the course of Thames, great woods of which Shotover and Bagley are the relics closing the horizon to the south and east. Though the two huge towers of its Norman castle marked the strategic importance of Oxford as commanding the river valley along which the commerce of Southern England mainly flowed, its walls formed the least element in the town's military strength, for on every side but the north it was guarded by the swampy meadows along Cherwell or by an intricate network of streams into which the Thames breaks among the meadows of Osney. From the midst of these meadows rose a mitred abbey of Austin Canons, which with the older priory of St. Frideswide gave Oxford some ecclesiastical dignity. The residence of the Norman house of the D'Oillis within its castle, the frequent visits of English kings to a palace without its walls, the presence again and again of important Parliaments, marked its political weight within the realm. The settlement of one of the wealthiest among the English Jewries in the very heart of the town indicated, while it promoted, the activity of its trade. No place better illustrates the transformation of the land in the hands of its Norman masters, the sudden outburst of industrial effort, the sudden expansion of commerce and accumulation of wealth which followed the Conquest. To the west of the town rose one of the stateliest of English castles, and in the meadows beneath the hardly less stately abbey of Osney. In the fields to the north the last of the Norman kings raised his palace of Beaumont. In the southern quarter of the city the canons of St. Frideswide reared the church which still exists as the diocesan cathedral, while the piety of the Norman Castellans rebuilt almost all its parish churches and founded within their new castle walls the church of the Canons of St. George. [Sidenote: Oxford Scholars]