I think you have to take this PR with a pinch of salt. Presently proceeding through the House of Lords is the Policing and Crime Bill. Clause 99 says:
The proper officer of Revenue and Customs may require any person entering or leaving the United Kingdom—
(a) to produce the person’s passport or travel documents for
(b) to answer any questions put by the proper officer of Revenue
and Customs about the person’s journey.
This is the subject of fierce debate this week as Customs Officers double up as Border Officers these days. Quite easy really - you just tell the Customs guy to look out for certain people for 'customs' reasons and then if thinks someone might be an illegal immigrant he can just tip himself off!
The Report stage of this Bill is on November 5th and it remains to be seen whether the Government will get it's way with 'passports in country'!