Headquarters and1 Electric Lights Company Dorsetshire Fortress Royal Engineers
ds No 3 Company Dorsetshire RGA
ds 'A' Squadron Dorset Yeomanry

Listed as Sidney Hall in the 1909 Territorial Year Book, the Headquarters and 1 Electric Lights Company Dorsetshire Fortress RE is described in Kelly, 1911, as ‘The Sidney Groves Memorial Hall, on the North Quay, [which] was erected by Sir John Groves in memory of his son Sidney, and was opened 18th April 1900, and presented to Holy Trinity parish; the building includes a drill hall for the Church Lads’ Brigade, 102 feet long by 60 feet wide, officers’ rooms, reading room, library, caretaker’s house &c.; at the west end of the main building are the head quarters of the Dorset (Fortress) Electric Light Co. (Royal Engineers), including officers’ and sergeants’ rooms, armoury &c.‘