Answer: The Taylor Committee, whose recommendations resulted in the 1986 Act, discussed this and were strongly against the head having any say in the choice of a successor. That Act as such did not forbid it, and neither so far as I am aware did any subsequent primary legislation. But I am advised that, although the wording refers to "a teacher or other employee",without specifying a selection panel, it is forbidden by part of a statutory instrument made under the 1988 Act as subsequently amended, which has the force of law. I have taken advice on this because of the slight lack of precision in the wording I have referred to.
The rule (contained in paragraph 7 of the Schedule to Regulation 14) states that if a teacher or other employee is present at a meeting concerned with the appointment of his successor, he shall not vote; and that unless the governing body so allows, he shall "play no part in the consideration or discussion of the matter in question" and shall withdraw from the meeting. A subsequent amendment a few years later removed the discretion of the governing body so that the person may play no part and must indeed withdraw from any meeting on the matter.
Even if this somewhat complex rule did not exist, however, I should strongly advise against any involvement of the head. There are two issues. One is whether it is legal, which I have covered. The other is whether a decision made by a body which includes the head is vulnerable in the courts to a challenge that the decision was made improperly. If, for instance, a decision were made with the participation of a teacher governor whom a challenger considered to have an interest in the matter "greater than the generality of teachers", that decision could be open to challenge.
In your situation it is particularly dangerous, since there is at least one internal candidate, someone who has worked closely with you. If you liked that person, and he or she were appointed, you might be accused by another candidate of having favoured him or her. If you had not had a good relationship you might be accused by the candidate, if unsuccessf ul, of prejudice against. In both cases there is a plausible claim and a motive to challenge.
Even sharing in the drawing up of a person specificati on is dangerous since you could well persuade colleagues to include a quality or type of experience which only you knew the candidate in question had or didn't have. In the one recorded case where a headteacher appointment was successfully challenged in the courts by an unsuccessful candidate, the issue was not whether the decision was right but whether it had been properly made. You are so exposed in your situation that I advise you not to volunteer any opinion on candidates when they visit the school and indeed suggest you tell the governors not to ask you.