EDDC current constitution page 196

Do be aware that you are likely to have fettered your discretion where the Council is the landowner, developer or applicant and you have acted as, or could be perceived as being, a chief advocate for the proposal. (This is more than a matter of membership of both the proposing and planning determination committees, but that through your significant personal involvement in preparing or advocating the proposal you will be, or perceived by the public as being, no longer able to act impartially or to determine the proposal purely on its planning merits.)

and page 197:

Don’t speak and vote on a proposal where you have fettered your discretion. You do not also have to withdraw, but you may prefer to do so for the sake of appearances.

 Do explain that you do not intend to speak and vote because you have or you could reasonably be perceived as having judged (or reserve the right to judge) the matter elsewhere, so that this may be recorded in the minutes.

 Do take the opportunity to exercise your separate speaking rights as a Ward/Local Member where you have represented your views or those of local electors and fettered your discretion, provided you do not have a disclosable pecuniary interest.. Where you do exercise these speaking rights:
– advise the proper officer or Chairman that you wish to speak in this capacity before commencement of the item;
– remove yourself from the Member seating area for the duration of that item; and
– ensure that your actions are recorded.

…..
Be aware that you should not speak or vote on any matter which you have discussed at Cabinet unless you have demonstrated there and can do so at the relevant planning meeting that you have not predetermined the application. …

…Do not take part in any planning meeting on a matter in which you may have been seen as advocating a proposal as a Cabinet Member.