Authenticate and request a user's timeline with Twitter API 1.1 oAuth

This morning I have received the dreaded 'The Twitter REST API v1 is no longer active. Please migrate to API v1.1.' error in a few of my web sites.

Previously I have been using javascript/json to make these calls to http://api.twitter.com/1/statuses/user_timeline.json? to display a timeline.

As this is no longer available I need to adopt the new 1.1 API process.

I need to do the following using HttpWebRequest objects not a 3rd party application:

1. Authenticate using oauth key and secret
2. Make an authenticated call to pull back to display users timeline