Shipbuilding had been mainly carried out in the Southampton area, but from 1495 naval work was concentrated at Portsmouth and mercantile trading at Southampton. The naval establishment seems to have been on a very small scale until Henry VIII came to the throne. The increased importance was, however, very temporary for Portsmouth was virtually abandoned in favour of Deptford, Woolwich and Chatham. The reasons advanced were vulnerability to French attack, bad communications with the capital and supply difficulties. It was not until the Commonwealth period that Portsmouth Dockyard was placed on "a reasonably permanent base." The author traces the development of the Portsmouth Dockyard from this period up until 1948 and concludes with a list of ships built at Portsmouth between 1650 and 1945."