This section applies if—
a Part 3 warrant is issued in respect of a person;
the certificate contained in the warrant certifies that a sentence has been imposed;
an undertaking is given on behalf of a category 1 territory that the person will be required to serve the sentence in the territory;
on the basis of the undertaking the person is not extradited to the United Kingdom from the category 1 territory.
The sentence for the offence must be treated as served but the person's conviction for the offence must be treated as a conviction for all other purposes.