They made a very simple job of it. Applying a Sikaflex, under the loose head of the bolt, on the helm roof. (Seeing the leak from the lower helm, I presumed I'd need wood checked or bolts tightened from in there. However, the leak was so acute it certainly came from the other end of the bolt, it being loose on the bridge roof with no covering left.)
Leaks can be very difficult to find the source of. Often when repaired they come back. I've heard of captains who track water with a hose to find the source of a leak. A ships integrity will withstand a passage with minor leaks like mine was. However it's essential to keep a manual with information of leaks for crew and passengers. Then identify the source of any leaks which detriment the passage with sinking and seal it.