**File Photos** * RICHARD BRANSON'S SOCIALITE SON ENGAGED British tycoon SIR RICHARD BRANSON's socialite son is set to walk down the aisle after proposing to his girlfriend. Sam Branson, who has previously been linked to singer Natalie Imbruglia, popped the question to his partner of seven years, Isabella Calthorpe, during a romantic trip to Madagascar earlier this month (Jun12). A representative for the pair tells Britain's Daily Mail, "They both felt the time is right. They have no firm plans as yet, as they want to enjoy their engagement for a few months." Sam's sister Holly wed on her father's Necker Island in the Caribbean last year (11) in front of British royals Princesses Eugenie and Beatrice as well as Kate Winslet, who is dating Branson's nephew Ned Rocknroll. (MJ/WNWCDAM/PAW) Isabella Calthorpe Channel 4 Frightfest photocall held at the Empire Leicester Square. London, England.