The 26-year-old signed a four-year deal with the Saints for a fee reported to be around £7 million.
He was unveiled on the club’s Instagram account with the song Celtic fans came up with for him, celebrating the player’s “fine” hair and the fact he “scores belters all the time”, dubbed over it.
It struck a chord with Celtic fans still coming to terms losing another influential player to the Premier League side.
Celtic took the opportunity to tweet Southampton and request that a royalty payment be made to the Celtic Foundation “on behalf of our exceptionally talented fans”.
Southampton responded with a donation on Wednesday morning, confirming it on Twitter.