Whitmarsh graduated from Portsmouth Polytechnic (now the University of Portsmouth) with a degree in Mechanical Engineering in 1980, and started work at British Aerospace (now BAE Systems) as a structural analysis engineer at its Hamble-le-Rice facility.
Whitmarsh ukończył Portsmouth Polytechnic (obecnie University of Portsmouth) w kierunku Mechanika i Budowa Maszyn w 1980 i rozpoczął pracę w British Aerospace (obecnie BAE Systems), analiza strukturalna inżyniera w jego obiekcie Hamble-le-Rice.