I can't see that your son has an 'insurable interest'. (Read through this lot if you want to attempt an understanding of what that actually means in law!
http://www.hmrc.gov.uk/manuals/gimanual/gim1050.htm ).
Therefore any declaration by him that he has such an interest (which, I assume, would be required for an insurance contract to come into effect) would render the insurance null and void and render him, together with his employer, liable to prosecution for 'fraud by false representation', contrary to Section 2 of the Fraud Act 2006. (Maximm penalty = 10 years imprisonment).
However I admit that I'm fumbling in the dark here (so I'd welcome the views of people like New Judge or Barmaid) but I certainly wouldn't put my name to any such contract of insurance!!!