Grace Kelly's glamorous granddaughter appeared to confirm her engagement to her film producer boyfriend as she joined Monaco's high society at a charity ball last night. Charlotte Casiraghi, 31, daughter of Princess Caroline of Hanover, looks set to tie the knot with the dashing Dimitri Rassam, 36, after a whirlwind year-long romance. The couple looked the picture of happiness as they arrived for the annual Rose Ball in Monte Carlo, with Charlotte debuting a glittering diamond on her ring finger. Charlotte's brother, Pierre Casiraghi, 30, and her half-sister, Princess Alexandra of Hanover, 18, also attended. Charlotte Casiraghi, 31, announced her engagement to film producer Dimitri Rassam at the Rose Ball in Monaco last night.