How can I retrieve keys left in boot of my centrally locked Mondeo?

As I am no longer in possession of the car's main key (irretrievable loss), I used the spare - and only other - key to lock and immobilise my Ford Mondeo Verona Hatchback. After opening the boot to shuffle some belongings, I inadvertatly closed the lid to, thus locking this key in (on a fob, with my house keys)! Can they be retrieved without my having to break a window? Please help.