[keycloak-user] problems getting started with tomcat

[Tim Dudgeon]

a couple of weeks back I posted about having problems getting started 
with tomcat, but not had any response.
The post is here, along with an example:
http://lists.jboss.org/pipermail/keycloak-user/2015-July/002652.html

I'm still struggling with this, and think I have followed the 
instructions here correctly:
http://keycloak.github.io/docs/userguide/html/ch08.html#tomcat-adapter

Basically I think I'm having problems with the valve not doing anything.
I have copied the appropriate keycloak jars to $TOMCAT_HOME/lib and a 
web app with META-INF/context.xml containing this:

<?xml version="1.0" encoding="UTF-8"?>
<Context path="/sampleapp">
     <Valve 
className="org.keycloak.adapters.tomcat.KeycloakAuthenticatorValve"/>
</Context>

and a WEB-INF/web.xml pretty well as described in the docs, but I'm not 
getting any authentication challenge.

Any ideas what's wrong?

Thanks
Tim