In the ELMy H-mode regime, a degradation of the plasma energy confinement enhancement factor at high density is observed in most experiments [1.2], in contrast with the positive density dependence predicted by the energy confinement global scaling. In JET, when the density is increased at constant input power, some reduction of the stored energy (10%) is observed [1]. As the density is increased further, the plasma usually makes a transition from the Type I to the Type III ELMy H-mode regime. This transition occurs when the pedestal temperature falls below a critical temperature, Tcrit, which is, at high density, independent of density [3]. The transition to Type III ELMs is accompanied by a further large reduction of the stored energy and often also by a decrease in density. Therefore, the Type III ELMy H-mode regime represents a confinement limit for high density ELMy H-modes. In the edge operational diagram ne-Te, Tcrit limits the best operating point in terms of the combination of high density and good confinement (Type I ELMs). If Tcrit does not depend strongly on plasma triangularity, d, increased d is likely to extend the operational space for Type I ELMs at high density, through the increase in pedestal pressure. Similarly, an increase in pedestal temperature for a given density could be expected at higher input power, PIN, hence increasing the achievable density in Type I ELMs. On the other hand, the ability to operate in the Type I ELMy regime is likely to depend on the lower boundary of the ELM cycle more than on the upper one, and effects of the ELM frequency, fELM, on the fuelling efficiency could also play a role. Due to the very limited PIN available in JET, in the majority of the high density ELMy H-mode experiments previously carried out [1], PIN (=Ploss, since the discharge is in steady state) was less than twice the predicted H-mode threshold power, PL-H, at the highest density. Previous JET results also showed that, at low density, where the critical temperature for the stabilization of Type III ELMs decreases with density (T µ 1/n), an input power Pin >2 PL-H was required to obtain and maintain the Type I ELMy regime at low d (d@0.2). A reduction of the power threshold for Type I ELMs with increased d was also observed at low density [4]. This paper presents the result of an experiment to study how PIN/PL-H and d affect the high density ELMy H-mode operational space in the Type I ELMy regime, that is, with good confinement.