Viscount Seaham (later 6th Marquess), became Lt-Col Commandant in turn, and was still in command of the unit when it transferred to the Territorial Force, before becoming Honorary Colonel. From 5 May 1866, the corps was officially allowed to include '(Seaham)' in its title, and in 1868 four new batteries were added from around the West Rainton area. These were originally to have formed a separate 5th (Rainton) Durham AVC, but the personnel raised were placed in the 2nd, and the new officers were gazetted to the 2nd on 24 June 1869. By 1870, the unit had reached a strength of 12 batteries, including batteries at Silksworth and Old Durham. From 1 April 1882, the Durham AVCs became part of the Northern Division of the Royal Artillery, changing to the Western Division in 1889, when the subtitle was added to the unit's official designation. As well as manning fixed coast defence artillery, some of the early Artillery Volunteers manned semi-mobile 'position batteries' of smooth-bore field guns pulled by agricultural horses. But the War Office refused to pay for the upkeep of field guns for Volunteers and they had largely died in the 1870s. In 1888 the 'position artillery' concept was revived and some Volunteer companies were reorganised as position batteries to work alongside the Volunteer infantry brigades. On 14 July 1892 the 2nd Durham Volunteer Artillery were reorganised as 1 position battery and 10 companies: No 1 Battery at Seaham Harbour and South Colliery Nos 2–4 Companies at Seaham Harbour Nos 5–6 Companies at Seaham Colliery No 7 Company at Silksworth Nos 8-9 Companies at West Rainton Nos 10–11 Companies at Durham (the Old Durham Bty moved to Gilesgate) The Seaham Colliery Disaster of 1880 killed 36 NCOs and men of the 2nd Durham AVC. In 1900, a new company was raised at Gilesgate and moved to Brandon in 1901. A cadet company was formed at Seaham in September 1898 but was disbanded in 1903. Between 1860 and 1908, some 2 per cent of the 2nd Durham AVC's men transferred to the Regular Royal Artillery. The Artillery Volunteers were transferred to the Royal Garrison Artillery (RGA)in 1899 and with the abolition of the RA's divisional structure in 1902 they were redesignated, the Seaham unit becoming the 2nd (Seaham) Durham RGA (Volunteers). Territorial Force When the Volunteers were subsumed into the new Territorial Force (TF) under the Haldane Reforms of 1908,