This is a HL7 FHIR server, and as you appear to be accessing this page from a web browser you are seeing a HTML version of the requested resource(s). You can also access this URL from a FHIR client as a ReSTful API call. For more details please see the HL7 FHIR specification.
<?xml version="1.0" encoding="UTF-8" standalone="no"?><NamingSystem xmlns="">
   <name value="NHS Number"/>
   <status value="draft"/>
   <kind value="identifier"/>
   <date value="2015-05-01"/>
   <publisher value="NHS Digital"/>
      <name value="Interoperability Team"/>
         <system value="email"/>
         <value value=""/>
         <use value="work"/>
   <responsible value="NHS Digital"/>
   <description value="NHS Number allocated to the patient."/>
   <usage value="A unique patient identifier for everyone registered with the NHS."/>
      <type value="uri"/>
      <value value=""/>
      <preferred value="true"/>
      <type value="oid"/>
      <value value="2.16.840.1.113883."/>
      <preferred value="false"/>