GRACE KELLY's grandson has filed a lawsuit against a man charged with assaulting him during a nightclub altercation earlier this year (12).

Businessman Adam Hock was slapped with four counts of third-degree assault after allegedly hitting Prince Pierre Casiraghi and three of his friends, including Paris Hilton's ex-boyfriend Stavros Niarchos III, following a confrontation at Big Apple hotspot Double Seven in February (12).

The royal was admitted to the New York Presbyterian Hospital, where he was treated for a swollen jaw and scratched face, and now he's taking legal action against those allegedly involved.

On Monday (16Jul12), Casiraghi filed documents at the Manhattan Supreme Court against Hock for causing personal injury, and also named the bar's owner, Jeffrey Jah, in the suit.

The 24 year old is also suing Hock's attorney Joe Tacopina and former lawyer Sal Strazzullo for defamation, according to the New York Post.

Casiraghi, who is the third in line to the Monaco throne, is the youngest son of Caroline, Princess of Hanover.

07/17/2012 12:04