Vicon KM-series trailed mower conditioners: Vicon was a major player with its Olympus and KM242 Swather in the 1980s. Then came the firm’s modular cutting deck GMT and GMV ranges in the early 1990s, followed in 1996 by the subjects of this article, the KMT2800 and its successors. James de Havilland assesses their merits as a second-hand buy