OK open to ideas here with this one :-

we have a mcb style mains board (crabtree from memory) which has an RCD
device built in. Normally when when for an example a bulb goes the trip
for that lighting circuit goes bit of a pain but we can live with it.
However yesterday and today has been a nightmare with the main breaker
tripping on average every two hours! No individual circuit goes and
throwing the break brings everything back to normal (apart from having
to reset the times on the cooker microwave stero etc!).

At a loss for any ideas. Nothing has changed regarding load no new
devices etc and its happened day and night so its not something we are
manually turning on or off.

any ideas where to start ?