Why are we called for passport interviews ...

[alterhase58]

... you might ask ... many applicants are surprised about this, after having been through the naturalisation mill.
This might explain:
http://news.bbc.co.uk/1/hi/uk/6370627.stm
Note IPS referred to in the article is now HMPO.

[vinny]

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Try.

[secret.simon]

It is worth noting that the passport interviews were called for all first adult British passport applications, including for those born British citizens and those who had already held British passports as children/minors.

Because even those born British citizens are called for these interviews, you will find this as a fairly common topic on forums oriented towards students, when one is likely to be applying for their first adult British passport, such as TheStudentRoom. Searching "TheStudentRoom passport interview" and similar terms in a search engine will give you a broader idea about these interviews.

When I naturalised, it was a compulsory interview for all first adult British passport applicants and I was lucky that I was able to arrange an interview with a passport office just down the road from my workplace.

Nowadays, it is a random selection from such applicants. But again, worth remembering that all first adult British passport applicants, including those born British citizens, can be called for such interviews.

[rv2010]

There's also these guidance notes for HMPO staff to help them decide who should or should not attend an interview:

https://www.gov.uk/government/publicati ... le-version

Of particular interest is this part (which probably applies to many people on these boards):
"If we have enough information from identity checks, we will not interview an adult customer applying for their first British passport when they ... were naturalised within the last 12 months and UK Visa and Immigration service’s records confirm the customer’s photo identity and personal details".