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Sorry I didn’t see that. I had two concurrent passports for a while. All it took was a letter from my employer saying that I needed two passports, that I had a lot of travel coming up an needed to have one spare so I could have one in an embassy getting a visa whilst travelling on the other one. Worked just fine
Does the UK system allow you to get extra pages tacked on? You can do this with a US passport.
― American Fear of Pranksterism (Ed), Thursday, 7 November 2019 19:54 (four years ago) link
I filled up a passport because I lived next to the Macau border and they stamped it every time I went in or out, so 4 times per trip, easy to do.
UK do not do the extra pages thing. Have not heard of getting two passports apart from people with duel nationality.
― mfktz (Camaraderie at Arms Length), Thursday, 7 November 2019 20:11 (four years ago) link
The guidance on renewing a passport might be helpful:
https://www.gov.uk/renew-adult-passport/renew
Specifically the section on unexpired visas - it suggests you "send your previous passport with the visa attached to it with your application. Your previous passport will be returned to you. You'll be able to use the visa if you carry both passports."
You might want to order a special 50-page passport while you're at it. My hunch is that the cost of renewing a passport will be no more than applying for a second one. From what I've read owning two passports is really only open to government employees or businesspeople who get it done through their place of work.
There's also an emergency travel document:
https://www.gov.uk/emergency-travel-document
One of the criteria is that "your passport has been lost, stolen, damaged, is full, has recently expired or is with HM Passport Office or a foreign embassy", but it seems you can only apply if you're outside the UK, it costs £100, and it sounds scary.
― Ashley Pomeroy, Thursday, 7 November 2019 23:39 (four years ago) link