When the Volunteer Force was subsumed into the new Territorial Force (TF) under the Haldane Reforms in 1908, the 1st Hampshire RE (V) became the Hampshire (Fortresss) RE (TF), forming part of Southern Coast Defences.
Together with the Regular No 4 Company, RE, at Haslar Barracks in Gosport, the unit was responsible for the coastal defence searchlights in the Portsmouth area, including the Isle of Wight and the three sea forts at Spithead (Spitbank Fort, No Man's Land Fort and Horse Sand Fort).