OK - the roof itself may have been finished, the collateral damage hasn't.
OH has been painting and sealing the barge boards.
When doing this, he see's that when one of the barge boards was screwed in, the screw went through the electricity supply cable to the house. The problem being that while the screw didn't go through the live cable it did go through either the earth or neutral cable. It's not possible to tell which it was. Earth, no problem, neutral, potential problems in the future

He contacts the joiner who did the barge boards as he didn't want to screw the joiner up with the main builder, without giving him a chance to redeem himself. Joiner & electrician chum arrived this morning, all went well till electrician had a few problems & OH made a few gentle suggestions (he's a physicist for f---s sake, oh and was certified for working with live electrics) the electrician got snotty and stormed off. It was decided that joiner would contact another chum who works for the power supply company. We'll see what happens............
S--- S--- S---