| The gatehouse is approached via a brick barbican, a defensive outwork furnished with arrow slits and end turrets. |
| To these engines the besieged opposed the first trebuchet, and another mounted in the barbican. |
| The purpose of a barbican was not just to provide another line of defence but also to dictate the only approach to the gate. |
| They had crossed Smithfield together, and Clennam was left alone at the corner of barbican. |
| The barbican at Walmgate Bar was undermined and explosives laid, but, the plot was discovered. |
| The exterior one, which is reinforced by a barbican, has 18 towers plus one with an octagonal base. |
