Posted: Wed Oct 4, 2017 4:01pm
It all depends what's tripping - whether it's the circuit breaker for the oven circuit, the earth leakage breaker, or the Iberdrola cut-off switch that operates if you exceed your contracted supply.
If it's the earth leakage breaker, there's a fault somewhere. However, I'd have expected this to trip immediately, not after a delay.
If it's the oven's circuit breaker, there could well be a different sort of fault, probably with the oven. It could even be that the breaker isn't the correct one - you should normally have a 16 amp blue breaker. It could even be a faulty breaker - that's happened to me once.
If it's the cut-off breaker, then you're exceeding the contracted supply. This breaker in your case should be 25 amps.
I disagree for once with what 271935 says about running multiple ovens. Ovens are power hogs. Without looking I don't know what my present oven draws, but the one I had in the UK drew about ten amps.