Problem with my oven, Blowing the master switch?

Question:I have a built in oven/grill (Zanussi ZBF 760). The hob is gas and separate to the electric oven/grill unit.

Clock works fine, however when I turn on the oven several mins later it blows the master trip switch leaving cooker circuit trip untripped.

This does not happen with the grill,

Could anyone give me some advice, please

Thank you

Answers:
What do you mean by the master switch? It sound to me like on of the elements have gone bad generating excess heat over time causing the breaker to trip. I would call an appliance guy not an electrician.