Could an employee subjected to derogatory comments on the basis that he or she is Welsh have a potential claim under the Equality Act 2010?

Yes. The Equality Act 2010 protects employees against discrimination and harassment because of race. To bring a claim of race discrimination, the employee must compare his or her treatment with that of someone who belongs to a different racial group. For the purposes of the Act "racial group" means a group of persons defined by reference to race, and "race" includes colour, nationality and ethnic or national origins. In Northern Joint Police Board v Power [1997] IRLR 610 EAT and BBC Scotland v Souster [2001] IRLR 150 CS the Scots and the English were held to be separate racial groups by reference to their "national origins" (but not to their ethnic origins), even though they both hold UK citizenship and both their national origins are also British. By extension, the Welsh would be a separate racial group to the English and the Scots, as would the Irish. It follows that an employee who is subjected to derogatory comments on the basis that he or she is Welsh would have a claim of race discrimination under the Act.