To restrict access to a web area, place the following in your virtual host config.

The details for LDAP settings can be found in the LDAP Settings of the Users and Groups menu

AuthName "Charnvel staff only"
AuthType Basic
AuthBasicProvider ldap
AuthzLDAPAuthoritative on
AuthLDAPUrl ldap://localhost:390/ou=Users,dc=charnvel,dc=co,dc=uk?uid # The user need to enter their uid (logon)
AuthLDAPBindDN cn=zentyalro,dc=charnvel,dc=co,dc=uk
AuthLDAPBindPassword # enter the read only LDAP password from Zentyal
Require ldap-group cn=webapps,ou=Groups,dc=charnvel,dc=co,dc=uk # User needs to be a member of the webapps group to authenticate.
#Require valid-user # User only authentication

When testing, it seems that LDAP lookups are cached with a TTL of 10 mins.