Using a foreign passport in the UK as a British citizen

You have not mentioned whether you have applied to the EU Settlement Scheme (both the Settled, and Pre-Settled statuses) or not when it was still possible to do with your non-British passport (this is a fairly common scenario for people who have naturalized as a British citizen after the EUSS system was set up, but before the general EUSS deadline of 30 June 2021).

If you have, then you should have a login to https://www.gov.uk/update-uk-visas-immigration-account-details where you can keep the details of your non-British passport or identity card updated in the EUSS (more precisely the UKVI) database. This would make it easier for you to travel with your non-British passport (or even with your ID card), as being in the EUSS/UKVI database would allow the Border Guard to establish your right to enter easier.

Note: While you cannot apply to the EUSS scheme after you have naturalized, if you actually do it before (like as a pre-condition to getting naturalized) the few benefits it give you, including the ability to travel by ID card seem to remain.

Source: I’ve done this myself – my British passport was just getting renewed and my EU passport has also just expired so it was up for renewal and the old ones were with their respective governments, so not in my hand. The only valid stuff I had was my EU ID card, and I had to enter the UK using that. The only very minor issue was with airline whose online checking tool only allowed ID cards for travel after clicking a checkbox that said "I confirm I have Settled Status" or something similar.

I used to work for UK Border Control but retired some years ago so what I say may not now be the up to date position.

That said, having more than 1 passport is very common and it is entirely up to you which one to use. You are not obliged to renew the British one if you don’t want to. However what matters is what you intend to do in the UK. With the exception of Irish passports which allow a general right to reside in the UK, all other EU citizens are now subject to conventional immigration control. So if returning to the UK to resume residence, you would need to demonstrate you had that right. Otherwise you might be subject to a time restriction and a prohibition on employment or even refused entry.

You haven’t said where you were born but assuming it was in the UK, birth in the UK in itself does not confer British nationality or even a right of residence, so having a UK birthplace in an EU document is not sufficient proof of the right to live in the UK. Additional documentation is required.

There used to be a document called a “Certificate to the right of abode” (issued by the Home Office) that you could get endorsed in a non British document, to show you had that right. That would enable you to pass through the UK controls without difficulty. However it costs more than renewing your British passport so you may not feel it worthwhile. You could also show the Immigration Officer your expired British passport as proof, but as has been said, that’s going to be a slower process. You also need to be aware that if you show an expired passport at check-in the airline may not carry you. So you would need to carry both documents.

I don’t have time to look up a proper reference for this just now, but the UK takes a fairly liberal line on the principle that citizens have a right to enter the country. Any proof of citizenship will do; there’s no obligation to use a British passport. If you come to the border with your foreign passport and it looks for some reason like they’re not going to let you in, you can establish through any means that you are a British citizen and they’ll let you in.

However, if you’re using your foreign passport to go in and out a lot, you may raise red flags as a potential overstayer. In this case you will indeed need to explain that you’re British, and the officer at the passport desk is not likely to welcome the extra work this will require. Doing this a couple of times is probably not going to cause any trouble, but I suspect that doing it regularly could be a bit of a hassle, probably less hassle than renewing your British passport.

If you try it, come back and post an answer to let us know how it goes.