Complex sentence: In 1996, MI6 is alleged to have paid a Libyan Al Qaeda cell to kill Colonel Gaddafi, al-Libi being allowed to stay in return for aiding the alleged plot, which was unsuccessful.
Split into simpler sentences: In 1996, MI6 allegedly paid a Libyan Al Qaeda cell to kill Colonel Gaddafi. Al-Libi would have been allowed to stay in return for aiding the alleged plot, which was unsuccessful.