Oh,,, That makes it allright then !!!
Serious breach of H&S I'd 've thought.
Years back , a multi-lock system was used at the Round Oak Steel Works and the consequences were dire if the procedure wasn't followed .
It started with the overhead cranes , of which there were many, and a caliper with numorous holes was fitted to the isolator if you were working on or above the crane rails.
Each trade/ contractor would fit their own lock to the caliper .