Sussex Yeomanry The Sussex Yeomanry was a yeomanry regiment of the British Army formed in 1794 , with its last remnants disbanding finally in 1999 . It was initially formed when there was a threat of French invasion during the Napoleonic Wars . Sussex Imperial Yeomanry . The Sussex Imperial Yeomanry was formed 14 June 1901 , as one of the Imperial Yeomanry regiments created to serve in the Second Anglo - Boer War in South - Africa . The Imperial Yeomanry regiments were disbanded in 1908 . World War I . During World War I the Sussex Yeomanry formed second ( 2 / 1st ) and third ( 3 / 1st ) line regiments . The 2 / 1st was formed in September 1914 , they were converted into a cyclist unit in July 1916 while part of 4th Mounted Division and remained in the United Kingdom until April 1918 , when they were moved to Ireland The 3 / 1st formed in 1915 , also remained in the United Kingdom until the unit was disbanded in 1918 . The 1 / 1st Sussex Yeomanry in 1914 were part of the South Eastern Mounted Brigade , 1st Mounted Division . In September 1915 the regiment was dismounted and moved to Gallipoli , landing at Cape Helles on October 7 , 1915 and attached to the 42nd Division . Within days of the landing the Regiment reported many men suffering from enteritis . While at Gallipoli they spent time in the trenches at Border Barricade and Fusilier Bluff . Along with the rest of the Army they were evacuated leaving the peninsula on December 30 , 1915 , arriving in Egypt in February 1916 . At this time the Regiment was absorbed into the 3rd Dismounted Brigade . A formation that was initially assigned to the defence of the Suez Canal and later moved to the Western Frontier Force where they were involved in the Battle of Gaza and the advance to Jerusalem . On January 3 , 1917 they were reassigned as infantry and formed the 16th ( Sussex Yeomanry ) Battalion , the Royal Sussex Regiment . They were then moved to France in May 1918 where they were involved in the Battle of the Somme in 1918 . Between the wars . On reforming the TA , the 14 senior Yeomanry Regiments remained horsed cavalry regiments ( 6 forming the 5th and 6th Cavalry Brigades ) while the remaining Yeomanry Regiments were re - assigned as artillery . In 1922 the Sussex Yeomanry was amalgamated with the Surrey Yeomanry and re - formed as the 98th ( Surrey and Sussex Yeomanry ) Brigade , Royal Field Artillery . World War II . During the Second World War there were 2 Regiments associated with the Sussex Yeomanry They took part in the Battle of France and the campaigns in East Africa , North Africa and Italy . Post war . In 1947 the Regiment was reformed as a separate Regiment . This reformation lasted until April 1 , 1967 when they were once again amalgamated with other Yeomanry Regiments to become the 100 ( Eastern ) Medium Regiment Royal Artillery ( Volunteers ) . They were again redesignated as the 100th ( Yeomanry ) Regiment Royal Artillery ( Volunteers ) in September 1976 . In April 1993 200 Battery was converted to 127 ( Sussex Yeomanry ) Field Squadron 78 ( Fortress ) Engineer Regiment Royal Engineers in support of 3rd UK Division . The 78 ( Fortress ) Engineer Regiment was disbanded on July 1 , 1999 as a result of the Options for Change restructuring programme . The title Sussex Yeomanry continues in use as the designation of one troop of 579 Field Squadron ( EOD ) . Part of 101 ( London ) Engineer Regiment ( Explosive Ordnance Disposal ) ( Volunteers ) , 1 ( Sussex Yeomanry ) Field Troop is based at Brighton TA centre . Colonels - in - Chief and Honorary Colonels . Colonels - in - Chief Honorary Colonels