The suburban lands which were successively granted to the Company were not protected either by the walls of Fort St. George or by the walls of Black Town, and it was accordingly necessary that special means should be adopted for their defence. The Company's military engineers devised the erection of small suburban forts ('redoubts'), block-houses, and batteries, which were to be mounted with cannon and to be in charge of an appropriate garrison, and were to serve as outposts for the protection of the outlying quarters of the city.
On the northern side of Black Town the batteries and block-houses were linked together by a thick-set hedge of palmyras, bamboos, prickly-pear, and thorny bushes, such that neither infantry nor cavalry could force a way through. Later it was decreed that the 'Bound Hedge,' as it was called, should be extended so as to encircle the whole city. The work, however, was never completed, for as late as 1785 an influential European inhabitant of Madras, addressing the Government on the subject of the insecurity of the city, wrote:--
"Was the Bound Hedge finished, no man could desert. No Spy could pass; provisions would be cheap. All the Garden Houses, as well as thirty-three Square Miles of Ground, would be in security from the invasions of irregular Horse."
Of the suburban fortifications the two largest were at Egmore and at San Thomé. Next in size were those at Nungumbaukam and at Pursewaukam. Of smaller works there were many. Of the fortifications at Nungumbaukam and at Pursewaukam all traces have disappeared; but of the larger ones at San Thomé and at Egmore interesting remains are still to be seen.
The remains of the San Thomé Redoubt stand within the grounds of 'Leith Castle,' a house that lies south of the San Thomé Cathedral. The remains are ruins, but the massive walls fifteen feet high and three feet thick, are suggestive of the purpose for which the redoubt was built. The 'Records' show that the San Thomé Redoubt, built in 1751, was a very complete fortification, with a moat forty feet wide, a glacis, and all the other works that are usual in respect of a well appointed building of the kind. That it was of a large size is to be seen in the fact that, when the French under Count Lally were besieging Madras, an English officer was officially directed 'to stay in St. Thomé Fort with the Europeans belonging to Chingleput, four Companies of sepoys, and fifty horse.'
The Egmore Redoubt was a good deal older than that of San Thomé. It was constructed in the days of Queen Anne. It was intended, of course, for the special protection of Egmore; but in those distant days when trips to the hills were unknown, even Egmore was a health-resort in respect of the crowded Fort St. George, and it was officially reported that the Egmore Redoubt might 'serve for a convenience for the sick Soldiers when arrived from England, for the recovery of their health, it being a good air.' The Egmore Redoubt was evidently a need; for the 'Records' tell us that on various occasions its guns were fired at the enemy. The enemy were for the most part horsemen of Haidar Ali or of Tipu, his son and successor; and in 1799 the year in which Tipu was killed, the need for the Redoubt disappeared. Adjoining the precincts of the Redoubt were the premises of the Male Asylum, an Anglo-Indian Orphanage, which required to be extended, and in the following year the Madras Government gave the Redoubt to the Asylum, and the two premises were turned into a common enclosure. In the beginning of the present century the Directors of the Asylum sold their Egmore estate to the South Indian Railway Company and removed to new premises in the Poonamallee road; and what remains of the Egmore Redoubt is now the habitation of some of the Railway employees.
The remains are of quaint interest. At some date or another the authorities of the Asylum had an upper story added to one of the military buildings, with the result that there is the strange spectacle of a row of windowed chambers on the top of a buttressed and battlemented wall, windowless and grim. The upper story has been built into the battlements in such a manner that the outline of the battlements is still clearly visible, and the building is a composite reminder of old-time war and latter-day peace. The whole of the lower part of the building, with its massive walls and its frowning aspect, is of curious and suggestive interest; and the ground around, which is extensively bricked, is a reminder of the fact that the Redoubt in its original form was large indeed. The place provides interesting material for antiquarian speculation.