Barlow 'treated' the crowd to a medley of Rat Pack hits at the Royal Albert Hall gig in aid of the Prince's Trust. 'Greatest Day', 'Never Forget' and 'Pray' (to which he performed a solo dance routine) were also on his set list reports Unreality TV.
Strictly Come Dancing stars Lulu and Jason Donovan joined Gary on stage as did hat-botherer Olly Murs for a rendition of 'Shine'.
Gary was also set to duet with his X Factor mentee Marcus Collins but he had to cancel due to a poorly throat. However, Marcus told Radio 1 he will make an appearance at tonight's concert "even if my voice breaks all the way".
Prince Charles and Camilla Parker Bowles will also be in attendance this evening, which makes sense seeing as Barlow's overseeing Charles' mum's birthday celebrations.