Fixing a Tarred Valley
Once again we find evidence of Neanderthal Contractors ruining an otherwise good slate roof. Tar is the Neanderthal Roofers best friend.
This solution which may stop leaks for a couple years ruins the valley and surrounding slates. Unfortunately, the couple years this fix lasts is usually long enough for the incompetent roofer to go out of business.
These are the steps to fixing a tarred valley.