The name of the island is derived from Platt of
Molesey who used it for growing withers. Boatbuilding began on the island in 1868, when Thomas Tagg, who had been running a business since 1841 on
Tagg's Island, about downstream, expanded by building a boatyard and house on the eastern end of Platt's Eyot. A waterworks and electrical works with a charging station were also constructed on the island; the latter was used to power electrically powered pleasure launches and canoes that were built on the island. Around 1904
John Isaac Thornycroft set up the Hampton Launch Works on the island, an offshoot of the
Chiswick boatyard that he had established in the 1860s. This boatbuilding works concentrated on cabin cruisers and speedboats, but the success of Thornycroft's operations on Platt's Eyot led to the award of contracts from the
Admiralty. A new and larger facility was built in
Southampton, which became Thornycroft's principal yard, but the Platt's Eyot yard continued to operate in both World Wars to build small naval craft. During the
First World War, in 1916 the Admiralty commissioned a new type of fast torpedo-carrying motor launch which Thornycroft constructed secretly in its Platt's Eyot facility. Four new boat sheds were constructed on the island, probably in the same year (though the date is disputed by some), to a design by Augustine Alban Hamilton Scott. They were built using the
Belfast truss system, developed during the First World War to roof wide structures such as aircraft hangars. Very few boat sheds were constructed using the technique, by the minister's Order in Council mechanism (after due notice in
The London Gazette and considering representations and whether to hold a local inquiry by the
London Government Act 1963). The change was an administrative exchange, in that
Thames Ditton Island transferred at the same time. On 3 May 2021, a large fire consumed the ex-industrial boat sheds. ==See also==