Can choose Commonwealth citizens in the UK

What is the reason that Irish and Commonwealth citizens are allowed to vote in general elections?

It should be noted that Commonwealth citizens are not considered "aliens" or "aliens" under UK law (British Nationality Act 1981, Part IV: 37) and are therefore allowed to vote under the law. An obvious example of this is our "State Department" being referred to as the Foreign and Commonwealth Office.

You have to remember that the Commonwealth was originally born as a bit of imperial management and was originally arranged as autonomous states still "loyal to the crown". Since the parliament was originally only an advisory body of the crown, any "subject" of the crown could vote or be elected to the chambers of parliament.

The United Kingdom only really accepted the existence of the Commonwealth in the 1926 Balfour Declaration, which so decided

Autonomous communities within the British Empire, on an equal footing, in no way subordinate to one another in their internal or external affairs, though united by a common allegiance to the Crown and freely linked as members of the British Commonwealth of Nations

Notice the wording of the text above, although they recognized the independence of these nations, they considered them, at least in part, as "communities within the British Empire".

The British have simply never changed the law or their position, despite the fact that the Commonwealth has little political importance other than "lip service" due to changing world events and has always recognized the citizens of the Commonwealth as at least partially separate from other foreigners. And there has been no significant movement to change that law.

While I can't find the interview anymore, I vividly remember an interview where current union leader Jeremy Corbyn said on camera the importance of protecting the franchise of Commonwealth citizens - if anyone can find the video , please post in the comments and I'll edit my answer to reflect it as such