T.O.D.
I've never been a big fan of Peter Sellers, though I do like BEING THERE very much.
I recall being on the set of THE PARTY a couple of times. Had a publicity client (Timothy Scott) in that one.
The first David Niven movie that comes to mind is THE GUNS OF NAVARONE, one of the great WW2 action films. Also his Oscar-winning role, SEPARATE TABLES.