The Haslar Barracks site was developed in 1802 as a permanent regimental infantry barracks within a clearly defined boundary wall.
In 1864 the site was converted into a military hospital as part of the first phase of reform to army hospitals following the Crimean War.
Additional buildings included a water tower, day room and covered colonnade linking the wards (formerly the barrack ranges).
In the 1890s the site was taken over by the Royal Engineers who have strong connections to the military defences in the borough and experiments and training in the use of searchlights and mines. These three phases, and the retention of the historic buildings associated with them in the scale of the buildings and their plan form, make this site of particular interest.
Haslar Barracks is a site of national historic significance due to its rarity by type, and its strategic role in the defence of the wider military establishments in the Gosport and Portsmouth area. It appears to be the only significant regimental infantry barracks’ complex that survives in England relating to the threat of invasion in the years leading up to the Battle of Trafalgar (1805): a crucial and nationally significant period, making the site of particular historic value.
The site has been transferred to the Home Office to be refurbished as an Immigration Removal Centre again, due to reopen in 2024.