BBC Radio 4 has a series of programmes called "In Our Time" which discusses major topics in history, science, religion, philosophy etc. Most of them are available to listen in the audio archive. The Christmas Eve programme discussed "The Samurai". Since it is the most current programme, you can catch it through the following link:
http://www.bbc.co.uk/radio4/history/inourtime/index.shtml
After a week or so, you'll have to find it in the archive.