James Corden has admitted that filming Carpool Karaoke with Sir Paul McCartney is his favourite ever moment on 'The Late Late Show'.

The 39-year-old comedian's in-car singalong segment has featured mega music stars such as Madonna, Sir Elton John, Katy Perry and Mariah Carey, but getting The Beatles legend in the passenger seat was a dream come true for him.

Speaking to BBC Radio 1's Nick Grimshaw, James - who is filming 'The Late Late Show' in London all this week - said: ''Tomorrow night we will be airing our Carpool Karaoke with Sir Paul McCartney which might be I think - it certainly is for me personally - my favourite thing we've ever shot on the show. It felt like a real thing and to round off what's been an epic week of shows for us really.''

James - who admitted he is currently suffering from hay fever - also reminisced about his performance for Comic Relief in 2009 when he appeared as his 'Gavin and Stacey' character Smithy, giving a motivational speech to the England soccer squad to inspire them to play better.

James said he owed it all to striker Peter Crouch for making the comedy sketch a success.

He explained: ''I tell you he weirdest thing about that entire sketch - we didn't know which players were going to be given. So we wrote the entire sketch in 20 minutes, we plotted it together and then we had this idea to end with trying to emotionally speak the words of the 'World In Motion' rap. And then we were like, 'How does it end? And then we looked at each other and we said, 'We've got to hope that they get into it, because if they don't respond and start going, 'Yeah,' then this has a terrible ending.

''And I will always so be grateful to Peter Crouch, because he was the first person that just went 'Come on Smithy!' And then they all got into it and then they left. We only had them for 19 minutes and that whole day just reminds me of just stomach-churning nerves, hoping to pull it off.''

While appearing on The Radio 1 Breakfast Show, James surprised listeners by answering the phones and played a prank on a girl who had given up her ticket to be in the audience for 'The Late Late Show' to attend a friend's birthday party.

James called her and challenged her on why she was not coming to the show, before confessing it was all a joke.