The main parties will usually have legal representatives to present their case and to cross-examine any witnesses.
Prior to the inquiry date, the Planning Inspectorate will expect to have received various documents from all parties that will be taking part in the appeal.
These may include statements of case and proofs of evidence from expert witnesses. Third parties may also take part.
The inquiry will be led by the inspector and will follow a formal procedure.
All parties will have the opportunity to present their case, and witnesses are likely to be questioned by the inspector and the other parties as to the evidence that they have presented.
Much of the evidence may be technical or specialist knowledge that needs to be carefully presented and understood by the inspector.
An inquiry may take one or several days, or in some cases weeks. The length of the inquiry will depend on the complexity of the case and the number of witnesses involved.
At some point during or on conclusion of the inquiry the inspector and the main parties will undertake a site visit.
A written decision is usually made several weeks after the inquiry.