A video purporting to show UK hostage Alan Henning being beheaded has been released by Islamic State militants. The Salford taxi driver was delivering aid to .\r<br>\r<br>David Cameron has promised to hunt down the terrorist murderers of the aid worker Alan Henning after jihadists posted video of him being beheaded online.\r<br>\r<br>Islamic State militants beheaded British aid worker Alan Henning in a video posted on Friday, triggering swift condemnation by the British and United States (US) .\r<br>\r<br>The distraught wife of Alan Henning, the British hostage threatened with beheading by Islamic State terrorists, has issued an emotional television appeal to his .
