Horsea Island

Horsea was originally two islands, Great and Little Horsea, the former large enough to support a dairy farm. In 1804 a Royal Powder Works was established on Little Horsea in connection with the gunpowder magazine at nearby Tipner; by 1849, however, it was no longer in operation, and no above-ground evidence of the site remains to be seen. The islands were joined to form a torpedo testing lake in 1889, using chalk excavated from Portsdown Hill, 1 km to the north, by convict labour. A narrow-gauge railway was constructed on the site by the army to distribute the chalk. Although the lake length was increased from 800 yd to over 1000 yd in 1905, rapid advances in torpedo design and range had…

The original island site continues to be used by the MoD, with a number of facilities on the site predominantly focusing on diving and underwater engineering. Infrastructure includes training facilities as well as workshops, decompression chambers and equipment testing capabilities. Organisations on the site include: The lake was used by Southsea British Sub Aqua Club in the 1950s, and later by many other clubs and private training agencies for underwater swimming and diving. However, civilian access is no longer permitted for security reasons.