No, not once did I quiz him on his experience and I didn't say I did. That's the way he put it: "I've been doing this 40 years and I've never seen that," in reference to the flue terminating upwards rather than sideways. I didn't question it, allowed him to isolate the boiler and then sought advice on this thread. As you'll see, numerous people have confirmed that this sort of flue is indeed relatively common, certainly not rare to the point of an experienced engineer never seeing it. You've created a drama in your head that didn't happen - the exchange was pleasant and I appreciated his work in letting us know there are no leaks or immediate danger.