how can i fix my ford mondeo mk3 2.0ltr tddi ?

hiya i have a ford mondeo mk3 2.0ltr tddi. got in the car to go to work and it was fine it was fine nearly all day parked up and left it for a while went to start it again and nothing happening just clicking the speedo and rev limiter goes all the way round to max did have dash light oil battery etc etc but now nothing at all ive tried changing the battery and its still the same can some one help please