I think Stephen just understands his history better than others and the response to his post is over the top.
There isn't any such thing as a British nation in reality. Britain is a union between different nations. That is the constitutional arrangement and the history of it. There is a lot of soft propaganda going on in the background; people are discouraged from thinking about or understanding their history and identity, particularly if they are natives of these Isles and especially if they are English. So ignorance is to be expected.
Those of us who are "British" - the English, Scots, Welsh, Irish - understand that whilst we have things in common and have been together for a long time, and have a shared history, that we are also different to one another. It runs deep. The history of Ulster shows this, and the long history of conflict between England and Scotland before the Union. The fact that there are devolved administrations, although England doesn't get to have one for reasons that might be discussed separately (modern politics and dishonesty being key ingredients).
There is kinship and there is animosity at the same time, amongst people who look very similar, are (more or less) fluent in the same language and customs, have lived together for thousands of years. And we are of course discussing only nationality here, not ethnicity, which is a whole interesting topic in itself.
I personally do not describe myself as British. I am English. I am not Irish, Scottish or Welsh, although I have plenty in common with them, relatively speaking, including genetically. I only use the word British when it is relevant to discuss our common history. E.g. we might talk about the British economy or the British role in WW1. I do of course hold a British passport and am a British citizen, but the word British is as much a convenient, administrative catch-all as it is a meaningfully real thing. It is a form of branding - a way to present the different peoples and nations abroad as one thing. I think those of us who are of these lands know this instinctively.
It becomes an increasingly meaningless term, whereas the words used for the constituent nationalities retain their value and force. The word British is like paper money that isn't backed by gold, or anything else; debased more and more by the effects of inflation.
So when you hear a person who has recently immigrated from a very different region and culture, or exists in a separate culture here as a result of that process, describing themselves as "British", you can see how it also forms a useful function there as a more nebulous construct to absorb and disguise very different peoples, cultures and identities. Then on to that vague branding exercise they will often hyphenate it with something else entirely. Pakistani British, British Muslim, or whatever. Sometimes different combinations are used by the one person, almost in a chameoleon fashion, like disguises, to suit the situation. But curiously never English, even when they were born and grew up here.
Ultimately, you will find out what a person really is when you get to know them and see which ideas, customs, history, people, places and things they really care about. That will reveal their true identity, underneath all the mumbo jumbo. As we know from other contemporary sillines and lies, like the 73 genders, there is always a common sense, factual truth once we see past the smoke and mirrors.
Worth mentioning that some people, particularly those who have been governing us, don't care about anything very much, apart from power and money, thinly disguised by intellectual nonsense. The globalists... who are a strange, parasitic cult unto themselves and "above" such considerations as those I have discussed.