James (Giacomo) Leoni, English architect of Italian origin. Apparently a Venetian, he was at the court of Elector Johann Wilhelm of the Palatinate at Düsseldorf from 1708. There he was influenced by the architect Count Matteo Alberti (?1660-1716), with whom he probably worked on the Elector's hunting-lodge, Schloss Bensburg, near Cologne. Alberti was an admirer of Inigo Jones, and it was Jones who also became Leoni's model; this is particularly evident in the earliest known designs made after his move to England c. 1714. Leoni made his name in 1715 with the publication of the first instalment of The Architecture of Andrea Palladio, the first complete edition of Palladio's I quattro libri dell'architettura to appear in English. He also produced The Architecture of Leon Battista Alberti (1726), a three-volume translation of Alberti's De re aedificatoria, illustrated by Leoni and with some of his own designs appended. By 1722, Leoni designed his most original house, Carshalton Park, Surrey, for Thomas Scawen. At that time his mentor appeared to be the Scottish architect and writer Colen Campbell (1676-1729). Carshalton's elevation is a version of Palladio's Palazzo Valmarana, but with some important differences. In 1725 Leoni made designs for Peter Legh's Lyme Park, Ches, and between c. 1729 and 1735 he rebuilt the 16th-century house in progressive stages around its courtyard. Leoni's style lends little credence to his claim to be Venetian. Clandon Park (?1731-3), Surrey, for Thomas Onslow, 2nd Lord Onslow, slightly resembles the Villa Garzoni by Jacopo Sansovino, and it displays a paneled pediment, which could have been taken from Venetian examples. Leoni would appear to be part of a Campbell school, a grouping of English neo-Palladian architects with a style different to that of Burlington, Kent and their followers. As Leoni was one of the few among them who could claim to have had direct contact with Palladio's own work, it is particularly remarkable that he should have chosen British architects for his models. Along with Alessandro Galilei and Niccolò Servandoni, Leoni is significant as one of the first Europeans to have been influenced by British architecture, instead of the other way round. //