The present invention relates to computerised trading systems and associated methods, particularly those that implement trades in basis trading where the two instruments have different and non-universally agreed pricing mechanisms and metrics, such as futures crosses in the European derivative markets. The present invention allows traders to enter orders expressed in terms of their own metrics. These orders are then converted to be expressed according to a standardised metric such that comparisons may be made and orders matched. Once matching orders are identified, these orders can be reported back to the traders, expressed in terms of their own metrics.