The building known as the Main Guard has a long and interesting history. It is the Headquarters of the Gibraltar Heritage Trust and is composed of offices, meeting room and library on the top floor and shop, stores and patio on the ground floor. The façade of the building that gives onto John Mackintosh Square today retains much of its original built fabric, the ground floor built before 1753 and the 1stfloor probably added after the Great Siege. It is delicately detailed with a central colonnaded loggia on two stories in the Doric order.
A prepared report by the architect J. S. Langdon described the condition of the Main Guard before the proposed repairs and alterations were carried out as follows:1
An interesting feature is the enlarged spacing between the central columns on the ground floor which was carried out as an alteration to the original in 1924 to allow the fire engine to be driven into the building when it was used by the Fire Brigade. These alterations also included the replacing of the original raised timber ground floor with a solid concrete floor (the original air bricks for the raised timber floor are still evident), the removal of the inner wall of the ground floor loggia, the heightening of the central wall arched opening and the replacement of the original ceilings with corrugated steel sheeting.
The condition of the façade is not bad considering the number of years of neglect and unsympathetic alterations, such as the enclosure of the ground floor loggia, telephone and electricity cables and brackets. Beneath thick layers of paint, the plaster or stone mouldings are still evident and the original casement windows, as seen on the Carter prints, are still in place on the upper floor.
Although it is not clear when exactly the building was constructed, the first references to it date to the middle of the 18th century.
We know that Dr Robert Poole, for example, visited Gibraltar in 1748 and stayed in a hotel on the "Parade", probably on the south junction with Main Street, where Griffith's Hotel was later situated. He writes:2
"A little below my lodging is what is called the Grand Guard House, which is one of the neatest buildings in these parts, though it is but low, being not but one storey high, which indeed is the common height for the buildings in the city... Before the guard house, a little upon the Parade, is the whipping post, where almost every day soldiers are brought to feel the scourge..."
At the time John Mackintosh Square was known as The Parade due to its function as a parade ground. In a plan of the parade made in 1750 by Thomas James (published in 1770) the building is clearly shown, labelled "Main Guard Room" with soldiers mustered outside it. It is also present in the Montresor 1753 plan and referred to as "The main guard". The building consisted of two rooms or offices at the front on either side of a foyer and a barrack room at the back. A small patio at the rear can also be observed.