Here are some lectures given by Walton in the past
httpv://www.youtube.com/watch?v=o26Ad-WdjOw&feature=player_embedded
httpv://www.youtube.com/watch?v=V6B2qTdacBY&feature=player_embedded
httpv://www.youtube.com/watch?v=CNn6Y4qDK7U&feature=channel
httpv://www.youtube.com/watch?v=oabDyyXxMdw&feature=channel
httpv://www.youtube.com/watch?v=Ntdf2QIMdMo&feature=channel
httpv://www.youtube.com/watch?v=folwJJTmXz8&feature=channel
httpv://www.youtube.com/watch?v=1BWiOo0bxGk&feature=channel
HT.