You say you have actual fuses in your consumer unit, so it is probably rather old. Is it a rented home?
I will guess that the thing that tripped is an RCD and has a "T" or "Test" button on it. The RCD is usually at least twice as wide as the other breakers or fuseholders.
Possibly it had not tripped or been tested for a long time and had become sticky. Now that it has operated under the fault, it has got unstuck.
I will guess that you have a smallish earth leakage from other appliances in your home, which are somewhere in the region of the current needed to make it trip, and now it has loosened, it is now tripping more easily. I will guess that the oven element in your cooker is quite old and the insulation has broken down with age (this is very common).
Try turning off the oven and all the elements or rings on your cooker, and unplug the kettle, iron, washing machine and any other "watery" appliances in your home. Switch off the immersion heater (if any) and the boiler at the wall. Turn off all the computers and unplug them. Turn off or unplug fishtanks, pond pumps, shed supplies and outdoor lights exposed to rain or damp. These are all devices likely to be raising the background level of earth leakage. This will probably take the total leakage below the tripping point.
Now turn one of them on and see what happens, then turn it off and try another. If the cooker still trips the breaker, then it will be whichever element is switched on. If it is any other appliance, such as the washer, it may be damp inside, possibly due to a leak, and you should have it PAT-tested and repaired. It might be a combination of several appliances.
However it might just be a general low level of earth leakage from numerous points, which add together to reach the tripping level. It is difficult to trace and deal with this is the wiring is generally old. It happens more often when there is only one RCD for the whole house, which is not now the preferred design.