The paper presents a constitutive modelling of the London clay based on the detailed laboratory knowledge gathered about London clay structure (Hight et al, 2007; Gasparre et al, 2007; Gasparre & Coop, 2008). Modelling was performed using a structured kinematic hardening soil model based on Rouainia & Wood (2000). It was found that a smooth elasto-plastic transition was required to avoid a spurious stiffness degradation response. Consequently, the initial model was modified following a procedure similar to that suggested by Grammatikopoulou et al. (2006). Parameters associated with soil structure and state variables for each lithological sub-unit of the London clay are presented. A good prediction of stress-strain, strength and stiffness behaviour in the small strain range is obtained in spite of the complex behaviour observed in laboratory. The significantly different mechanical behaviours of the lithological sub-units, arising from differences in structure, are adequately reproduced.