http://www.theregister.co.uk/2006/03/31/ippr_irregular_migration/
John Lettice
"Overseas visa applicants have their biometrics read as part of the application and can therefore be positively identified on entry to the country. Because their biometrics are on record, the chances of intercepting and deporting overstayers increases, at least in theory. Biometrics are also taken from new asylum applicants, so again they're on record and can theoretically be nicked and returned. Non-UK EU citizens will in the future have to have an ID card if they're resident in the UK for longer than three months; this one won't be in place for a while yet as compulsion can only be applied to them when it is also applied to UK citizens (EU law talking here), but it's an important aspect of the 'ring of steel' in that it provides a means of differentiation"
