The ride to abode visa is important and since the new regulations came in employers can pick up big fines for employing people who are not eligible to work in the UK even if they believed they were. The level of checking is going up to the extent that even those who have never had to prove their right of abode (native born Brits) are now being required to provide the evidence.
Apparently some jobs worth has decided that asking those that obviously appear or sound foreign to provide evidence whilst not asking those who do not look or sound foreign could be classed as discrimination.