Timothy Gowers on combinatorics.  

Youtube link: [Topics in Combinatorics][1]

Sean Prendiville on additive combinatorics. His lecture is somewhat scattered on the webinar page. He also provides lecture notes.

Youtube link: [Fourier Methods in Combinatorial Number Theory][2]


  [1]: https://www.youtube.com/c/TimothyGowers0/videos
  [2]: https://www.youtube.com/c/WebinarinAdditiveCombinatorics/videos