Read somewhere this morning that "they never got closer than 15 miles" which is 3 times the ATC separation standard. Looks like 5 miles is good enough for Airservices in TIBA airspace.
Ask any controller how often he/she uses 5 miles and they`ll say, basically never as i like to sleep at night! There is a time and a place wher i may use something between 5 and 10 miles but headings or speeds or both will be pegged.
From memory the Lear and a JST aircraft were at the same level ( FL240?) and never got closer than 15nm. Where they converging, diverging or just 15nm abeam as they passed? Either way it doesn`t sound good.