As the refusal letter of the context question states, the papers were decided to be a false representation because they are either

* used by an imposter [as in: he is not the person the papers claim to be]
* has been obtained fraudulently [as in: the information given to the issuing country were not correct]

The UK authorities reasoned, that your statements were wrong and that as a result the papers must either belong to somebody else or were obtained fraudulently. Possession of such ID papers (including passports) is a crime under [Identity Documents Act 2010, s.6 b & c][1]:

> It is an offence for a person (“P”), without reasonable excuse, to have in P's possession or under P's control—
>
> (b)an identity document that was improperly obtained,
>
> (c)an identity document that relates to someone else,

and s7:

>(1)For the purposes of sections 4 to 6 “identity document” means any document that is or purports to be—
>
>(c)a passport issued by or on behalf of the authorities of a country or territory outside the United Kingdom or by or on behalf of an international organisation,
>
>(d)a document that can be used (in some or all circumstances) instead of a passport,

As such, the possession of the papers under a fake name for a state that does not offer dual citizenship but not having repealed the one before makes the second papers **improperly obtained** or belonging to **somebody else**, which is a crime punishable with up to 2 years in the UK, as Section 7 C explicitly says "passport issued by a country outside of the UK"

  [1]: https://www.legislation.gov.uk/ukpga/2010/40/section/6