This thesis presents the results of an experimental assessment of masonry flexural bond strength. Since there is insufficient experimental data on key performance requirements for bond between units and mortar, investigations into the development of bond and flexural strength across a range of masonry units for both traditional and new mortar types, reflecting the recent changes in European standards, were conducted. In order to demonstrate the performance of bond between unit and mortar, the latter ranging from weak to strong, a practical bond wrench testing rig was developed for use with couplets and stack bonded prisms. This involved carrying out investigations into existing designs and revaluations using up to date modelling techniques. The result is a new bond wrench applicable for use in laboratories and on site.