From: DMcG - PM
Date: 17 Nov 18 - 05:13 PM
It is valid English form, Iains, though less common than the 'Am I'. I am sure Nigel will be along to explain it shortly.
Sorry, no. I cannot find a valid construction that would make: I am the only one who finds it amusing the Tory blue is derived from the Scottish part of Union flag? into a valid question, despite the question mark at the end.
For it to be a question you would need to change the start to "Am I . . ." or, add something at the end, such as "I am the only one who finds it amusing the Tory blue is derived from the Scottish part of Union flag, am I not?
You might get it accepted in spoken English as then tone of voice can be added, which helps indicate from the start that it is intended as a question. That doesn't work in print. It would work, possibly, if we introduced the Spanish practice of starting sentences with inverted punctuation.

As to the use of "Union jack" I also used to argue that it was not strictly correct. But I have since been informed that it is perfectly valid. The following page shows that not only does the usage pre-date the term "jackstaff", but that it also has parliamentary backing. Flag institute.org
I still usually term it the Union flag, if only to avoid starting long discussions.