single/double MCB

[Spark123]

But without the more direct link between the two mechanisms, would one of them tripping cause the other one to switch off via the levers?

I'm assuming that the OP's electrician just linked the levers...

I assumed that too,
when an MCB trips there is little force behind the lever - the lever actually delatches and is only sent to the off position by means of a small spring. I imagine this is primarily so it doesn't take your finger off if you close an MCB on a short circuit. The force behind it is not sufficient to operate a second MCB via the lever hence the reason for the internal link.

 

[JohnW2]

...when an MCB trips there is little force behind the lever - the lever actually delatches and is only sent to the off position by means of a small spring. I imagine this is primarily so it doesn't take your finger off if you close an MCB on a short circuit. The force behind it is not sufficient to operate a second MCB via the lever hence the reason for the internal link.

Indeed - and, as I've said, I think there is a reason for that. If there were a more solid link between the 'switch' and the lever, then it would be possible by brute force (or if some external factor 'jammed' the lever) to hold the 'switch' in the 'on' position when it was meant to have operated due to overcurrent.

Kind Regards, John

 

[SimonH2]

Indeed, that's the "trip free" element which is there specifically to prevent someone holding the lever to override the protection. It's a fairly safe bet that without it, there would be a lot of "bits of wood, etc" holding circuit breakers closed In much the same way that some people consider that if a fuse bows, it's because it's too small - and the fix is a bigger fuse/thicker wire until it doesn't blow.