The government has now announced that headteachers need not possess any qualifications to teach any more. Their argument is that the government prizes autonomy over regulation.
However, it will surely be odd for the "head teacher" to be unable to teach given this potential lack of qualification. (It is also a matter for debate whether any hiring committee would choose to support candidates for such posts lacking such a central qualification.)
So why do it? It's yet another move towards the privatisation of education (and not merely higher education) in the United Kingdom by the coalition government. If teaching qualifications were no longer necessary, then the potential pool of applicants expands widely. It will become possible for those in business with no experience in the classroom to become the head teacher of local schools.