Next year will be it's 150th birthday!
The EPD report notes that in 1862:
Plans for the construction of a Barracks Block and Officers Quarters on the Central Police Station site are approved. Construction is complete 2 years later. The architect for the design is unknown, though Charles St. George Cleverly – then Surveyor of Hong Kong – probably had a great deal of input.
When it was completed in 1864, the building had three floors (ground / first / second). Later, another floor was added to make a total of four. That extension work was finished in 1906.