Consumer unit tripping and hard to reset

I had a power cut this morning. After a lot of experimentation, it seems to be related to the washing machine.

The thing that confuses me is that when we power the washing machine the master circuit breaker in the consumer unit trips. It then refuses to reset. I have every plug I can find in the house disconnected, and every switch turned off. It still refuses to reset.

It seems like after enough banging my head against a wall, and slowly trying to reset the master circuit breaker, it’ll give in. It takes a while though, and I have no idea why it eventually gives in, and even whether it will in the future.

Does this suggest that the master circuit breaker switch in the consumer unit needs replacing? Or perhaps there’s some leakage between earth and live and it just takes some time for that to ‘drain’ out of the system?? I’m obviously guessing here!!

I can’t exactly try many experiments with the washing machine as when it dies it’s a pain to get power back.

I tried changing the fuse in the washing machine plug just in case. That made no difference. Surely that fuse should have blown first? I also tried adding in an rcd between the washing machine and the plug socket – that also didn’t help and the main fuse went. Why could that be?

Any advice or suggestions really appreciated. I have an electrician booked in but the next available date is a few days away – and I’d also like to understand the issue a bit too!

Many thanks,
Dave.