A deep man-made ditch was dug on three sides and the south was defended naturally by Minster Pool.
In 1322, during the crisis involving Thomas, Earl of Lancaster, the chapter under royal pressure ordered the immediate clearance of the ditch and the completion of the west tower of the south-east gate.
At the south-east corner, there was a parapet along the top of the wall and a projecting turret, which survive as part of the later St. Mary's House.
Three interval towers were placed on the east wall, two of them incorporated in Langton's palace and the third on the site of the later Selwyn House.
There was a drawbridge, still in existence in the earlier 18th century, which crossed the outflow of water from Minster Pool, and also a wicket for pedestrians.
The increased fortification by Royalists occupying the Close, late 1642 to early 1643, included a complete encircling of the fortress cathedral with a moat.
The cathedral authorities with a certain following were for Charles I, but the townsfolk generally sided with Parliament, and this led to the fortification of the close in 1643.
[citation needed] Brooke's deputy John Gell, took over the siege[2] and the Royalist garrison surrendered to him two days later.
[3] In April of the same year (1643) Prince Rupert led an Royalist expeditionary force from Oxford to recapture Lichfield.
Unable to defend the Close, Colonel Russell, the parliamentary commander of the garrison, surrendered on terms to Rupert on 21 April.
[4] The cathedral suffered extensive damage: the central spire was demolished, the roofs ruined and all the stained glass smashed.