!..Burnt our MCB at busbar end..!

[mark ju]

or is there a more sinister explanation?

Yes there is in fact a sinister explanation for this.
It is obvious to me that extra terrestials are using your distrubution board to channel their radio signals to their home world.
This can be avoided by turning the DB off at the main switch for twenty four hours. Wrapping it in tin foil will also help.
Ignore all other comments, these are forum users just trying to set your mind at ease. i dont do things like that.

 

[markc123]

mark ju, lol ?

 

[oldtimer]

Also if inside the CU its good practice to check the connections and I mean check not overtighten