‘Treacherous assassination’: Who was Saif al-Islam Gaddafi?

Saif al-Islam Gaddafi, former Libyan leader Muammar Gadaffi’s most prominent son, and his number 2 between 2000 and 2011, was killed by “four masked men” in his Zintan home in what his political team blasted as a “cowardly and treacherous assassination”. But who was he?