Practice interceptions of civilian aircraft has been on the list of prohibited intercepts since back in the 60/70s
I don't think that there can be many ex-Wattisham fighter crews who haven't intercepted the 'Norwich flier' on a few occasions!
I don't think that AirUK ever complained though. But a chum and I were once flying back from Turnhoos to Norwich in an elderly AirUK F27 - only to be intercepted by an F4 from our own squadron.....
Night 'Profit' often jammed the Neatishead Fighter Controller, so a few airliners found themselves being intercepted on such occasions!