Present automobile development is keenly focused on measures to reduce the CO2 output of vehicles. Plug-in hybrid electric vehicles (PHEVs) enable grid electricity, which is clean in tail-pipe emissions terms, to be utilised whilst the on-board electrical storage has sufficient charge. MAHLE Powertrain and Protean have jointly developed a plug-in hybrid demonstrator vehicle based on a C-segment passenger car. The vehicle features Protean’s compact direct drive in-wheel motors with integrated inverters on the rear axle and retains the standard gasoline engine, and manual transmission, on the front axle.To support this one-off prototype, a flexible vehicle control unit has been developed, which is easily re-configurable and adaptable to any hybrid vehicle architecture. The unit operates using software developed by MAHLE Powertrain to achieve a fully configurable vehicle control unit (VCU), intended to provide a rapid and cost effective platform for the development of demonstrator and niche volume vehicle fleets.This paper describes some of the challenges, and solutions, associated with the vehicle conversion, including key vehicle integration topics, such as the CAN interface, vehicle control strategy, and the cooling system.