Diesel fuel injection pressures have increased steadily on heavy duty engines over the last twenty years and pressures as high as 300MPa are now possible. This was driven by the need to control toxic exhaust emissions, in particular particulate emissions using advanced in-cylinder combustion strategies. With the introduction of efficient aftertreatment systems for both particulate and NOx emissions control there is less demand for in-cylinder emissions control especially considering the drive for improved fuel economy. In this paper we consider the benefit of high fuel injection pressure for a number of emissions control strategies with different balances of in-cylinder and exhaust aftertreatment emissions control. A test program was undertaken on a single cylinder heavy duty research engine installed at the University of Brighton, in collaboration with Ricardo. The engine was fitted with the Delphi F2E fuel injection system capable of 330MPa injection pressure and multiple fuel injections. The engine intake system was configured to give independent control of the intake pressure and EGR rates, achieving rates of up to 50% at high engine loads. The benefit of high injection pressure was investigated under a number of strategies for achieving Euro VI emissions levels. The trade-off of controlling NOx emissions using EGR rate and aftertreatment on engine performance and Total Cost of Ownership (TCO) was investigated. Finally, the benefit of a simple split injection strategy at high rail pressure was studied.