how to wire in a A42A Smeg Cooker?

A friend kindly gave us her old A42A Smeg electric cooker with a gas hob for our new kitchen. An electrician came and sorted out the mains wiring for this 5KW cooker but unfortunately when the cooker is turned on, it trips the circuit and most of our lights go off downstairs....and we've had to resort to using a camping stove !! Any ideas what the problem may be ?Is it worth us calling out a SMEG expert or should we say bye bye to this oven