Regis Philbin took part in guest host week on CNN’s Piers Morgan Tonight programme last week and who better to have as a guest on that show than Regis’s old pal David Letterman?

Letterman actually asked to appear on the show when Regis told him he was guest-hosting, which is very unusual as Dave doesn’t normally appear on many TV programmes other than his own.

Dave talked about a lot of personal things on the show including his relationship with his wife Regina & his son, how he felt about going back on air after the 9/11 terrorist attacks and what he thought about the late great Johnny Carson & getting to perform standup comedy on Carson’s Tonight Show.

Watch the interview in full: