<P> (b) Harbour defences to remain in charge of British care and maintenance parties . Certain mooring buoys to be retained for use of His Majesty's ships . </P> <P> Accordingly, even after the establishment of the Irish Free State, the Royal Navy continued to maintain its presence at Spike Island . Spike Island remained under British sovereignty until 11 July 1938 when, pursuant to the Anglo - Irish Trade Agreement of 25 April 1938, the territory was ceded to Ireland . The hand - over ceremonies were attended by senior military and political figures, including Éamon de Valera and Frank Aiken . </P> <P> Following its handover to Ireland, the island's installations were renamed Fort Mitchel - after John Mitchel, nationalist activist and political journalist who was held on the island for a time . (Similar Treaty Port fortifications at Fort Camden and Fort Carlisle were similarly renamed to Fort Meagher and Fort Davis respectively .) The island remained the site of a prison and military base (for the regular Irish Army, the FCÁ and later the Navy) for some time . Late into the 20th century it was used as a youth correctional facility . On 1 September 1985 inmates rioted and, as a subsequent Dáil committee reported, "civilians, prison officers and the Gardai on the Island were virtual prisoners of the criminals". During the riot, one of the accommodation blocks, Block A, caught fire and is known as the Burnt Block . This prison facility closed in 2004 . </P> <P> The island also had a small civilian population; a small school, church and ferry (launch) service to Cobh served the population . The island is known locally for having excellent earth for growing crops . The civilian population has since left the island however, with many previous residents moving to nearby Cobh . </P>

When did spike island close as a prison