What makes a belief "protected" under the Equality Act 2010?

In our fortnightly podcast, David Hossack and Kerri McGaff discuss the Employment Appeal Tribunal case of Thomas v Surrey and Borders Partnership NHS Foundation Trust and another, in which the EAT considered whether "English Nationalism" could amount to a protected belief in the context of the claimant, an agency worker, having been dismissed prior to the expiry of his fixed-term contract.